I have a 19" tv and a dish network box that I want to mount to the wall. The thing I need help with is to how to make it move up and down the wall. My kid has a loft bed and we want to make it so she can watch tv in the up position when she is in her bed and in the down position when she is sitting down below it. Any help on this construction would be greatly appreciated. Also, need it to move safely because my daughter is 8. Thanks.