Calipers are a measuring tool designed to measure thickness, width, diameter or depth.
The calipers are somewhat fragile, so do use them with care. If damaged, their accuracy may be compromised.
Turn on the calipers by pressing the On/Off button. Close the calipers completely. If they do not move, check to see that the knob on top has been loosened. It should turn freely. If it does not, someone has over-loosened or over-tightened it. Press the Zero button to zero out the reading. Open the calipers and measure.
The main jaws beneath the display are for measuring width or thickness. The pointy area is for measuring things such as the thickness of the center of a screw, not counting the threads, while the thick flat part closer to the slide will let you measure including the threads, or to get a flat, straight measurement of thickness on something. The top jaws above the display are for measuring inside distances. You can use them to measure inside a pipe or a cutout. You will notice a piece of metal protruding from the bottom of the calipers. This is to measure depth. Rest the bottom of the slide against the lip of an object, then open the calipers until the metal rod touches the base/back of the hole. The reading will tell you the distance from the tip of the rod to the bottom of the slide.
To turn off the calipers, press the On/Off button and put them away.
The calipers are normally found around the laser cutter as they are frequently used to check the focus height.