The description of Winmau Laser Oche:

The Winmau Laser Oche is not mounted on the floor, but on the wall. By mounting the oche on the wall, you can aim the handy laser exactly at the right distance from the dartboard on the floor. This means you don't have to attach a sticker or oche to the floor, making this a handy product for darters who do not want to edit the floor with a sticker, glue or screws.