level lets you cross check accuracy by turning the level to compare to your marked measurements These small handheld bubble T-levels can be permanently mounted to a counter in your RV or on your furniture / machinery so you can always verify if it is still level (Note when mounting with screws, don’t screw too tight as to warp the levels body) Use when hanging pictures or other decor Very useful when leveling your RV or items in your RV Attach to the tongue or back bumper of a trailer or camper hitch to check for level Attach to pool tables or ping pong tables for accurate level play Use on machine tools ensuring level when using Magnetism can be adsorbed on iron, without screws. Use when leveling telescopes or cameras or other tripod mounted devices Each level has two screw holes for mounting and a flat back Some like to use double-sided tape on the back Each level consists of 2 liquid filled vials marked for easy read on a plastic triangular backing Small levels are so convenient to keep in your tool bag or on the go bag also as it takes up so little space and weighs so little The holes are provided for screwing to a surface permanently, but some use the holes to turn these into a string line level.