Sarrus Linkage
A well-known example of an overconstrained mechanism is the Sarrus mechanism, which consists of six bars connected by six hinged joints.
A general spatial linkage formed from six links and six hinged joints has mobility
and is therefore a structure.
The Sarrus mechanism has mobility M=1, rather than M=0, which means it has a particular set of dimensions that allow movement.
Read more about this topic: Overconstrained Mechanism