The most common spot of contact is the fetlock area. Sometimes you need to trim the hoof out of balance by lowering the outside hoof wall. Often a square- toe shoe on the front will help. On the rear a square-toe shoe with an outside trailer will work. Many things can be done to help a stumbler.
Forging means the hind shoe strikes the bottom of the front shoe on the same side.
Sometimes you can hear the shoes hit each other at a trot. To help stop forging, you need to speed up the front feet and slow down the rear feet. To do this, increase the angle of the front feet by shortening the toe and use a light shoe with a square toe or rocker toe. On the rear feet you can decrease the angle of the hoof by leaving the toe a little long and using a longer shoe that extends out behind the heel of the foot. A square-toe shoe with an outside trailer and heel calk on the rear will also work.