Correctly positioned inlet valves will ensure trouble-free vacuuming over the many years of service that will be received from a central vacuum system. The hose must be able to reach every corner of the house and go around furniture to get there. Curtains, cupboards and ceiling corners all must be reached. Central locations such as hallways, beside doors and adjacent to the bottom of staircases are ideal. Areas such as behind furniture or behind doors should be avoided. A 9m string or the hose itself can be used to help plan the layout. If working with 1:50 scale blueprints a 18cm string can be used to represent the hose.