When the baby is in the carrier, the baby's weight puts tension on the fabric, and the combination of fabric tension, friction of fabric surfaces against each other and the rings combine to "lock" the sling in position. This type of sling can adjust to different wearers' sizes and accommodate different wearing positions easily: the wearer supports the baby's weight with one hand and uses the other hand to pull more fabric through the rings to tighten or loosen the sling.
Ring slings may be padded or unpadded at the shoulder, have padded or unpadded edges or "rails", and the "tail" of the sling may be open or closed. Some "hybrid" ring slings have curved seats sewn into the body, similar to the seam in a pouch. Ring slings are most closely related in use to the Mexican rebozo, the rings take the place of the knot.
Whether a user will prefer a padded or unpadded sling, closed tail or open tail, simple or hybrid body is highly individual and often simply a matter of taste. Ring slings are available in a variety of fabrics ranging from lightweight cotton calicos to silk brocade. Tencel, linen, hemp and rayon have also been used. Most common are homespun fabrics, lightweight twills, dupioni silk, and other fabrics with good tensile strength and a fair amount of diagonal "give". The rings may be nylon, aluminum, steel or other materials, but it is important that any materials used be of sufficient strength and that multiple layers of stitching be used to connect rings to fabric, as several recalls of ring slings have been caused by faulty rings (welds breaking) or stitching (insufficient stitching such that if a thread broke, there was no redundancy). Most rings used by manufacturers are either designed specifically for baby carriers, designed for high-tension situations like marine rigging or for securing heavy livestock. Lightweight craft rings should not be used. Fabrics which cannot safely hold a seam without fraying or tearing should not be used. Excessively slippery fabrics should be avoided.
Another significant point of variation is found in how the rings attach to the cloth, commonly referred to as "shoulder style". Basic shoulder styles include gathered, pleated, "hot dog" or "center fold", pouch-style (folded in half) and many variations. Which is more comfortable for a given user may depend on body shape (whether the user has rounded or square shoulders), sling fabric (some fabrics will only be comfortable with padding, others work better in a gathered, unpadded style) and user preference for a wider or narrower spread.
Ring slings can be used from birth through toddlerhood, but many parents find that heavier, non-mobile babies are easier to carry in a two-shouldered carrier such as a wrap or mei tai (see below) when carrying will be extended. However, for short-term use, or for toddlers and mobile babies who want to be picked up and set back down often, ring slings can be ideal. Ring slings are also considered very good for breastfeeding, their adjustability allows them to be lengthened to allow easy access to the breast, and they can then be re-adjusted quickly when nursing is done. Ring slings are often the carriers of choice in the first months of life, when babies are small and nurse frequently.
Sometimes called "tube", "pocket" or "ringless" slings, these are generally formed by a wide piece of fabric sewn into a tubular shape. Simple, or fitted pouches do not have rings or other hardware. Adjustable pouches may adjust with a wide variety of methods, including zippers, snaps, buckles, clips, rings (these are usually considered hybrids), drawstrings or velcro. Most pouches have a curve sewn in to shape the cloth to the parent's body and hold the baby more securely than a simple straight tube. The wearer slips the pouch over the head and one shoulder, sash-style, creating a pocket or seat to hold baby in. The learning curve is short; most people find that they can learn to use the pouch quickly.
A properly-fit pouch can be used to safely wear a baby from birth to toddlerhood. Pouches are ideal for situations in which babies are frequently being removed from the pouch and put back in, for older children who do not want to be carried long but are heavy enough to be difficult to carry in-arms, and for young, small babies who are not heavy.
As with most one-shouldered slings, pouches are not ideal for long wearing of heavy babies, as the asymmetrical weight distribution can create back pain for the parent. The better a pouch fits, the more evenly it is spread across the shoulder and back, and the more suitable the fabric, the better a pouch will be for longer periods of use or heavier children. Proper fit generally means that baby is not sagging away from the parent's body, is not lower than the parent's waist or hip, and is not held uncomfortably tight.
Wraps (sometimes called "wraparounds" or "wraparound slings") are lengths of fabric (usually between 2 metres and 6 metres, or 2.5-7 yards long, and 15-30 inches wide), which are wrapped around both the baby and the wearer and then tied. There are many different carrying positions possible with a wrap, depending on the length of the fabric. A baby or toddler can be carried on the wearer's front, back or hip. With shorter wraps it is possible to do a one-shouldered carry, similar to those done with a pouch or a ring sling, although most carries involve the fabric going over both shoulders of the wearer and often around the waist to offer maximum support. These slings are the most versatile, but have a longer learning curve.
There are two main types of wrap - stretchy and woven.
Stretchy wraps are generally made of knits such as jersey or interlock. Polyester fleece and wool jersey are sometimes used for carrying babies in cool weather. It is easy to 'pop' babies in and out of a stretchy wrap. This can be easier for the wearer as the sling often remains tied on and the baby is lifted out and put back in as required. Stretchy wraps are popular for carrying young babies but the stretch can mean that they are not as comfortable for the wearer once baby starts getting heavy. Different brands and fabrics vary radically in the amount of stretch, and in general, the more lengthwise stretch, the less supportive the carrier will tend to be for a heavier or older baby. Several factors influence stretchiness: carriers with any spandex or lycra content will tend to be very stretchy, carriers which are 100% cotton or other natural fibers will tend to have less lengthwise stretch. Woven wraps are pieces of woven fabric of varying thickness and are available in a wide choice of colours, patterns and materials. Natural fibers are usually chosen, with cotton being by far the most common, but hemp, linen, silk and wool are also used. A variety of weaves are used. Most common are homespun or handwoven fabrics with simple over-under weaves, twills and jaquards. Most weaves provide some give or stretch diagonally. This allows the fabric to better conform to the baby and to the wearer's body. Thinner fabrics, while cooler, may cause pressure points for the wearer when used for long periods of time. Thinner fabrics are also less forgiving when less-than-perfect wrapping techniques are used.
Traditionally, the Chinese mei tai was a square or nearly square piece of cloth with parallel unpadded straps emerging from the sides of each corner. It was traditionally secured by bringing all the straps together in a twist with the ends tucked. The mei tai did not become well-known in the United States until 2003, when several designs that added padding, a longer body, longer top straps and a more "wrap like" tying method were created and made popular. A variation on the traditional mei tai was popularized in Australia in the 1960s. There are now hundreds of different brands of mei tai available with a variety of features, but the longer straps, taller body and wrap-style tying method are found in almost all of them. Mei tais are suitable for front or back carries with children ranging from birth to as heavy as a parent can support (usually between 35 and 45 pounds is the upper limit of comfortable wearing, but in emergencies and demonstrations, small adults have been worn. Wraps can be used through the same weight ranges.)
The podaegi (also spelled podegi and pronounced po DEG ee with a long "o", a hard "g" similar to the "g" in "golf" or "go" and a long "e") is a Korean carrier with a medium to large rectangle of fabric hanging from a very long strap. Traditionally the rectangle is quilted for warmth and wraps around the mother's torso, while the straps are wrapped snug under the baby's bottom and tied around to the front to support and secure the baby on the mother's back. Western interest in the podaegi style has led to new wrapping methods which do go over the shoulders, and to narrower "blankets". Variants of this shape include the Hmong carrier and the Chinese bei bei. The structure is similar, but usage can be very different. Hmong carriers and bei beis are both customarily used with over-the-shoulder wrapping and often have stiff sections which help provide head support or block wind, but their traditional, minimally padded or unpadded narrow straps limit their popularity among Western users. Western variants with more strap padding, less stiffener and other modifications are emerging.
Traditional babywearing in Japan was done with a wrap carry, using an obi (sash). In the 1940s, a carrier known as the onbuhimo became popular. Similar to the Hmong and Mei tai carriers, the onbuhimo has long top straps and a rectangular body. But at the bottom of the rectangle, loops or rings allow the top straps to be threaded through and tightened, while the straps are tied at the waist. The body is much smaller than the bodies of most mei tais and other Asian-style carriers, and the onbuhimo is traditionally used on the back. Variations may have stiff headrests or padding in the body.
Traditionally, baby slings and carriers were simply adaptations of whatever a culture normally used to carry anything heavy. Baskets, calabashes, animal skins, wooden carrying structures, all have been adapted to carry infants and children. Inuit mothers continue to use the packing parka or amauti to carry children up to two years old. In the west, this phenomenon has resulted in a variety of carriers based on camping backpacks (see below).
Historical photographs of indigenous peoples show babies worn in sashes, baskets and nets hung from the parent's forehead. Cradleboards and carriers hung from one shoulder like a purse have also been documented in several cultures.
Modern structured hip carriers, soft structured carriers which can be used on front or back, structured front packs and hard-framed backpacks are also used. Hip carriers may be closely related to ring slings or they may be more closely related to a mei tai, and several different types of fasteners are used in different models. Most of the soft structured carriers are loosely based on the traditional mei tai, with buckles, padding and clips added.
It is important to note that while structured carriers and other "purchased" carriers are popular, almost any sturdy piece of cloth can be turned temporarily or permanently into a baby sling or wrap. Bedsheets are often folded lengthwise and knotted, rebozo style. Four to six yards of soft, lightweight cotton fabric can be used as a wrap. A sweatshirt can be knotted sling-style or used to stabilize a "piggyback" back carry for an older child. There are a number of websites which provide how-to information on these improvised carriers.
NOTE: Risk of suffocation can be lessened by positioning infants correctly in the carrier, checking on baby often, avoiding positions which force the chin to the chest, supporting the back with a pillow in horizontal carries, and avoiding extra cloth, especially blankets, in the carrier.
Baby falling out