Each unit has a strong self adhesive backing; therefore no tools are required to install. A wide range of pole diameters can fit between the rollers of each unit:The adhesive backing sticks best on hard smooth surfaces such as tile, glass, metal, marble, and wood; and the backing can be non destructively removed from such surfaces. It can even stick on surfaces with a small amount of texture such as dry wall or even painted surfaces; but you should only attach the units to such surfaces if you never plan on removing them. For drywall, you will tear the paper off the dry wall if you plan on removing a unit; and for painted surfaces, you will remove the paint if you try to remove a unit. These units are real workhorses. You can yank your cleaning pole right out of the holder without any concern about the backing coming out of the wall.