The use of chairs as props in acrobatic activities falls into three broad categories: balancing, vaulting and contortion.
In chair balance acrobatics one or more acrobats balance on one or more chairs. The chair(s) may be balanced on other objects and/or on just one or two legs while the acrobat(s) themselves may also perform balancing acts on the chair.
The chairs used in balance may have notches cut out or extra pieces of material added to allow them to be stacked at otherwise unstable angles.
In chair vaulting the acrobat jumps or tumbles over the chair. Sometimes the chair is used as a launching platform and sometimes it is carried by the athlete while performing the vault.
Chair contortionists use the chair as a prop for moulding their bodies around.