A fuse splitter. It is designed to connect an additional device without cutting the car wiring. Choose any line in the fuse box, which is not particularly used and on which you can hang an additional device, for example, it can be a cigarette lighter. Remove the fuse from the block, and in its place insert this adapter. And already in the adapter insert the removed fuse and a new one (through it will go a new plus to the additional device).