Hang heavy objects on plaster walls by driving a nail into a stud behind the plaster or using an appropriate wall anchor. Prevent chips and cracks in the plaster by predrilling holes before inserting a nail. Molly bolts and toggle bolts are available with ratings up to 50 pounds. Avoid driving nails into the wooden lath, as it vibrates and breaks the keys, the expanded plaster that surrounds the boards and holds the dry materials in place.
Unpointed molly bolts require drilling a hole the same diameter as the unexpanded barrel of the bolt. These anchors are a better choice for lath and plaster walls than pointed molly bolts, which eliminate the need for drilling but are for use with drywall. Push the molly bolt into the hole and tap the screwhead to seat the flange. Once it is flushed with the wall, use a screwdriver to tighten the screw, causing the metal barrel to expand behind the plaster and spread the weight of the object over the back of the plaster. Loosen the screw slightly to support the object.
Metal toggle bolts also require boring a hole into the wall. The toggle threads onto a long nut. It is spring loaded and expands once it clears the plaster. Tighten the bolt so it supports the object. After you insert a toggle bolt into the wall, removing it requires loosening the bolt so the toggle falls into the hollow cavity. To reattach the bolt to the wall, you must supply a new toggle.