The tang-type buckle (also called pin buckle) is a locking mechanism for a watch strap.
In a pin buckle, holes are punched in the longer part of the strap, while the actual tang-type buckle is attached to the other part. The buckle itself consists of the mandrel which is passed through the hole to secure the desired length, a spring bar and a metal bracket in U-shape, which prevents the mandrel from sliding back out of the hole.
Buckles are used mainly in leather straps of all price and quality classes, but they can also be used in textile straps. Tang-type buckles of high-quality watches are adjusted according to the material of the case and usually provided with the logo of the manufacturer or other identification.