Two-prong lacing needles are a type of hand-sewing needle with two prongs that are used for sewing with leather lace. Typical needles have an eye where the thread is passed through and secured. This can be tricky or impossible with some leather laces, and the lace, once tied into a knot by the needle eye, would b too large to pass through the lacing hole in the leather.
Two-prong lacing needles have two prongs under spring tension instead of an eye. The prongs are separated and the lacing material slid between them. When released, the tension between the prongs holds the lace flat, and in place. This helps it maintain a thinner profile when passed through the stitching holes, especially diagonal ones.