New, Unused These are special tacks designed to be hammered into the bottom of sliding doors (fusuma and shoji) to improve their sliding. They can also be used to adjust the height of a door by hammering them into one side, correcting gaps. Installation involves making a hole with a drill or awl and then inserting the tack. 【Product Specifications】 Material: Plastic Size: 17mm diameter, 1.8mm thickness Shaft (insertion part) diameter: 3mm 【Installation】 With a 2.5mm drill hole, they can be installed with just finger pressure.