Caliper with locking button

Existing calipers including electronic digital-display one, mechanical vernier one and mechanical pointer one utilize screw to lock slide and its operation is inconvenient and needs two hands. The caliper of the present invention utilizes self-locking button, rather than screw, to lock slide. Depressing the self-locking button can lock the slide onto the main rule, and after reading depressing itfor the second time can unlock the slide for sliding freely. The caliper is convenient owing to its single-handed operation.