The Scotch Yoke Mechanism, a.k.a the Slotted Link Mechanism is used to convert linear motion to rotary motion, and vice versa.
Requires one 608RS Bearing. Assembly is pretty straight forward, but a pdf diagram is included. The pieces press fit together, and are a tight fit, glue/adhesives are optional.
An animated diagram of the mechanism can be found here, http://507movements.com/mm_093.html