Parachutes are manufactured in circular, square and rectangular shapes, among others. The earliest parachutes were circular and flat, which made them very unstable. Circular parachutes are now designed in a more conical form, while square and rectangular parachutes are more parabolic.
Circular parachutes that do not have holes in the back edges cannot be steered. By cutting holes just above the back edges, a circular parachute receives some forward motion and gives its operator a measure of control. Circular parachutes are commonly used for cargo drops. Modern square parachutes can be maneuvered very effectively and are preferred by skydivers. The cruciform design of a square parachute eliminates oscillation, which was an early problem with the design.