Most animal skeletons provide a rigid set of elements that meet at joints (articulate) to transmit muscle forces for movement and body support. They also enable many animals to manipulate their environment by digging burrows, building nests, or constructing webs to catch food. Animals have evolved three types of skeletal system: hydrostatic skeletons, exoskeletons, and endoskeletons. All three types of skeleton have rigid elements that resist the pull of antagonist sets of muscles.