Over the course of the shoeing interval, the hoof grows in length and broadens at the bearing edge, i.e., the horseshoe becomes too short and narrow  This development has to be borne in mind when selecting the size of shoe.The old horseshoes should only be used as a rough guide for size: The actual selection should be based on the size of the freshly trimmed hoof. The horseshoe should be selected so that the branch-ends cover the angles of the wall and do not project beyond these by more than the thickness of a horseshoe.

In cases where no size is an ideal fit, one can switch to another brand as sizes differ from one manufacturer to another. If this is not possible, then an experienced farrier can shorten the branch ends of a shoe that is too big by rasping them back or extend a slightly short shoe by stretching the branches.

The same problem is encountered when dealing with mismatched feet. Wherever possible the same size horseshoes should be used for both hooves and one shortened and the other stretched accordingly. Major differences in the circumference of the bearing edge (one contracted hoof, one flat hoof) can usually not be sorted out that easily, as stretching the shoe too much would make it too thin and would displace the nail holes too far to the back, making the last nail difficult or impossible to place. It may however be possible to rasp back the branch ends of the shoe that is too large. If the mismatch is extreme, then one may have to resort to using shoes of different sizes.