the appropriate angle for holding a staple gun up to a lock would be just the way you would hold it if you were going to put in a staple, the fingerlever cocks a spring, and trips it to fire a hammer in the direction of the staples points, this is kinetic energy going perpendicular to where you want it for a pickerpecker, but the hammer strikes so hard that you can mount a probe on the front outside of the staple gun and by drilling a hole in the clamshell case of the stapler, you can see that hammer go by, and insert a piece of the end of the probe so that as the hammer comes by, it strikes this end of the probe at a right angle to the direction of the hammer, as the probe end is cammed to an angle to take the strike from the hammer. (Hope someone is able to see the idea clearly, in spite of my explanation)

The concept is to have a probe orientated in the same direction as a staple is aimed and yet struck by the hammer in a way to make it bump perpendicular to the directionof the hammer, not so hard to do. and the way the stapler is held over the lock, to position it for the strike is more natural, the stapler could also have a bridge foot to place over protruding cylinders. three rubber points to steady the stapler in place while using it