Four Bar Mechanism
Google



You can move red or green ball for different arrangement. Now you can also change length of linkages. Note that when ball is moved to a point where this mechanism can't handle, rightlinks will be separated from rotating link. However end of right links will try to reach to tip of rotating link. This is because left links uses forward kinematics reach action.

I will start adding linkage mechanisms. First linkage will be a Four-Bar Linkage. All mechanism can be broken down into equivalent four-bar linkages. They can be considered to be one of fundemental mechanisms. These mechanism has many aplication in mecanical operations.
Grashof's law is applied to four-bar mechanisms.