A standoff is used in mechanics and electronics to separate two parts from one another. Standoffs can be many shapes and sizes and made of many different materials. Insulating standoffs may keep two parts from touching each other, thereby preventing an electronic short. Cable thumbscrews are often screwed into standoffs on the back of computers.
Standoff sizes are usually measured by the Unified Thread Standard. Size 4-40 is used to secure cables to external computer ports, and size 6-32 is used for motherboard mounts [1].
Dell, Inc. refers to standoffs that receive thumbscrews as "hex nut screws" and measures them with the Metric system.