Many sandal makers do line leather straps with nylon or canvas to add strength and prevent stretching, especially for long-lasting wear. For midsoles, materials like cork, neoprene, or canvas can help reinforce thin soles while adding comfort. A tongue depressor can work as a basic shank, but thin plastic or metal offers better support. Little upgrades like rubber outsoles, soft leather insoles, and clean strap edges can make handmade sandals both durable and worth the effort.