Brilliant piece of kit. Very, very easy to use - simply press the little red On-Off button, place the base of the Digi-Pas on whatever surface you want to measure, and the display panel tells you the precise orientation, correct to one tenth of a degree. It's neat, small, pleasantly tactile, remarkably accurate, and almost addictive - it's so easy to use, and so accurate, you may well find yourself wandering round the house with this little gadget in your hand, checking just how horizontal or vertical your doors, shelves, pictures, floors, walls and everything else really are. Sadly, Amazon say (on 10th May 2014) that this item is no longer available. That's a great pity, as it really is useful, as well as remarkably modestly priced. IMHO, it would be well worth your while to hunt out an alternative supplier on the net.