The floor press is a tried and true exercise for working through sticking points in the bench press, from midpoint to lockout. The limited range of motion allows for the lifter to focus on the "top" of the movement and focus on any problems in that portion of the lift.  The floor press is performed exactly the same as the bench press, except you lat on the ground instead of a bench.  For those with bad shoulders, the swiss bar's neutral grip can help alleviate some of the pain.  Adding chains, as Dave does in the video, increases the weight at the top of the movement, making the lockout more difficult.  It also looks really awesome.