Most 3D printer use a heated bed to make sure printed objects stay in place (amongst others).
The principle is based on keeping the object at a certain temperature, so that temperature differences between printed layers will not cause “warping” and even pop your object loose from the bed … and as a result of that screw up your print, and in bad situations even start dragging your object all over the place. (reference)
The time it takes to heat a bed however can take a long time, and frankly, I’m not that patient. So I use a super simple and cheap trick to speed up the heating process of the heated bed. It’s pretty much free and easy to use. I assume this will work for all 3D printers that print with plastics like ABS, but I have only used it with a LeapFrog Creatr so far.