If you want a successful glue-up, it's very important that you get the clamp pressure in exactly the right spot: directly in line with the parts being glued. Applying pressure out of alignment — off to one side or another — will twist the parts you're assembling, and you'll end up with a crooked project. This must be avoided because a glue-up is one of those irreversible construction tasks. A leg and rail assembly that includes a reveal, where the rail is stepped back from the face of the leg, is a great example.

As shown here in the photo, instead of simply pushing the clamp pads against the legs, insert a pair of pressure blocks between the pads and the legs. These pressure blocks should be squared up and float freely between the clamping pads and the assembly that you are building. (Don't be confused by the wooden clamping pads attached to the clamps.) The pressure blocks are directly in line with the rails and guarantee that the inside faces of the legs will seat squarely against the end grain of the rails.