This application solves a couple of problems that the owner of a home gym faces.
First, it is not always practical to drill holes in your garage floor, especially if you are renting. The fact that the platform weighs about 450 pounds when finished makes it a stable base for your uprights.
Second, garage walls are often uninsulated allowing sound to travel to the neighbors during early morning workouts. Quite often, the hardest sounds to block are the low frequencies that travel through the floor. By padding the area that the plates will land, you dampen these vibrations and avoid complaints from neighbors. Even the thin garage walls can take care of any residual clanking sounds caused by dropping weight.
The sound and vibration dampening is accomplished by stacking sheets of carpet padding below the lifting surface. In order to accomplish this dampening while still providing a stable lifting surface, 2 sheets of plywood, sandwiched together, float over the carpet padding, just below the horse stall mat.
2×4′s are stacked together to provide a firm support to attach the upright bases using 4 1/2″ long, 1/2″ lag screws.
2×12′s are attached to studs on the wall to provide a mounting surface for the standard pullup bar and Dirty South bar.
In this case the uprights reached above the rafters allowing the crossmember to be placed up there providing a higher attachment point for rings.
The end result is phenomenal home gym with a W-4 that even be used early in the morning without waking up the neighbors or your spouse.