Leather shoes generally fall into two categories: closed-upper shoes and sandals. Sandals can be further classified into fully open styles, styles with closed front and back sections but open sides, styles with closed toes and open heels, and styles with closed heels and open toes. Closed-upper shoes include slip-on, laced, high-top, and low-top varieties; appropriate shoe lasts must be selected during the design process to ensure the shoes meet standard specifications.
For instance, the allowance for a fully open sandal last is smaller than that for a closed-upper shoe last. If a sandal last is used to design a closed-upper shoe, the mid-section will be too loose and the forepart too short; conversely, if a closed-upper last is used for a fully open sandal, the forepart will be too long and the sides too narrow. Therefore, while sandal styles sharing the same structure as closed-upper shoes can utilize closed-upper lasts, fully open sandals require specialized sandal lasts.
The ball girth of a slip-on shoe last is half a size smaller than that of a plain-toe shoe last; a slightly smaller girth ensures the foot is held securely without sliding forward, allowing the shoe to stay snug against the heel while walking. In contrast, laced shoes require plain-toe lasts to avoid excessive pressure on the instep at the ball girth; thus, careful selection of the last is essential.
High-top lasts feature a larger top opening, whereas low-top lasts have a smaller one. Using a low-top last for a high-top shoe makes it impossible to put on due to the narrow opening, while using a high-top last for a low-top shoe results in a loose fit at the opening, causing the shoe to slip off the heel.
The outsole is a primary component of a leather shoe, bearing the full pressure of the body during walking and physical activity and maintaining direct contact with the ground. Consequently, material selection must account for durability and thickness, as well as resistance to flexing and abrasion.
The outsole is closely linked to the shoe's construction-such as through-stitching, pressed forepart, wrapped heel, edge binding, wrapped sole, welt, tucked-in upper, or cup-sole designs-with each structural method requiring specific design considerations. The outsole design is based on the insole pattern; factors such as the thickness of the upper leather and lining must be taken into account-allowing for more margin with thicker materials and less with thinner ones-while also considering material loss during edge skiving and grinding.