Applying a bandage properly is demonstrated in this short video. A well-padded bandage needs to fit snugly enough (with the absence of wrinkles) to prevent it from slipping. If the leg bandage slips, it will annoy the horse but worst case scenario it slips, bunches and creates a pressure point on the back of the tendon.
This occurrence can precipitate a so-called “bandage bow” or tendon damage. Equally, a bandage bow can be caused by a bandage that is too tight.