This sliding keyboard holder serves its purpose quite well, although the mouse shelf is a bit too small, and the space for the keyboard might not fit some larger keyboards. Note that the front sticks out about 4cm in front of the desk when it is pushed in. Don't even think about trying to attach this if you can't turn your desk or desktop upside down! If you can turn the desk over, it's easy to drill holes and insert the screws, although the screws supplied were too long for my desktop which is 15mm thick.
The method for raising and lowering it to the 3 different settings is very awkward, and you might have to turn the desk over again to do it. Furthermore, if the supports are close to a table leg, you won't be able to undo the screws, and you'll have to take the whole thing off and start again. All in all I wasted about 4 hours installing and adjusting this thing, but it is usable.