Diameter: 1/4 Length: 2-1/2 Material: Stainless Steel Thread Size: 20 (Coarse) Hardness: 18-8 Type: Hanger Bolt Application: Overhead Box of 12. A hanger bolt is a headless fastener that has machine screw threads on one end and self-tapping threads on the other designed to be driven into wood or another soft substrate. Often used for mounting legs on tables.