Works in different situations and can be placed on a table. A screw makes it easy to attach and remove. Most importantly, it forms an exact 90 degree angle. Keep in mind that these and most other 90 degree clamps will not fit. They are simply designed to hold 90 degrees. You need to make sure the ends are tight for a solid connection. One star off because there are 3 packs, not 2 or 4.