Edging is a climbing technique involving the placement of the very edge (either inside or outside edge) of the climbing shoe on a sharp hold. Edging is the most simple and most common approach for standing on holds but, even so, requires some practice to obtain the very best footing. On smaller holds, it becomes something of an exercise in precision.
An alternative to edging is toeing-in, where the toes are placed on the hold. This requires strong toes but might be preferable on very small holds, particularly in small pockets.
Another alternative is smearing, where the ball of the foot is, literally, smeared onto the surface of the rock in absence of any definite holds. Here one relies upon friction created at the sole of the shoe.