A Straddle Tilter has forks that lower and lay in between the front support frames or outriggers (the frame that has the front load wheels). The purpose of this design is to allow for the use of closed bottom pallets and containers (pallets/containers with an enclosure at the bottom). 

A Fork-Over Tilter has forks that lay on top of or “Over” the front support frames or outriggers.  This design is for use with open bottom pallets and open bottom containers.