Grounding box for connecting an antistatic bracelet. According to EN 61340, the wrong system for grounding an ESD bracelet is to connect it directly to the pad due to resistance addition.
The box is placed under the table, usually under the worktop or on a structure. If you are right-handed, place the box on the left and wear the bracelet on your left hand. If you are left-handed, place the box on the right. This gives your "better hand" more room to move, work and manipulate.