A Goodyear welt is a type of construction used to make a shoe more durable and long-lasting. It involves stitching a strip of leather, rubber, or synthetic material to the welt (the insole of the shoe) and then to the sole. This construction method creates a very strong bond between the welt and sole, which makes the shoe more water-resistant and increases its lifespan. Additionally, the welt can be replaced when it wears out, which makes the shoe even more durable.