uPVC Door Restrictors. We at Windoor hardware components carry a vast range of uPVC Door Restrictors to suit every application. There are three main category of door restrictor coupled with different levels of security. Firstly, the concealed restrictor which is available in two versions, there is a heavy duty restrictor with a metal arm which is located in an aluminium channel by means of a nylon friction block. This uPVC Door Restrictor enable its owner to adjust the resistance of the door leaf and its opening arc.