Slide joint
From Transformers Wiki
A slide joint couples two members while allowing them linear motion along a single axis relative to one another. In Transformers toys, this motion must sometimes be partly restricted to allow joints to remain in one or more configurations. This restriction is often provided by friction or by a sprung tab that fits into a notch.
When a slide joint allows one member to slide into and be partly or wholly concealed by the other, the joint is said to telescope, after the similar joints of a collapsible spyglass.
