Guide cross section Guide sizes which are available:- For a 77mm Lathed Door : A = 90mm or 75mm B= 35mm For a 55mm Lathed Door : A = 55mm or 70mm B= 30mm If you are calling for a price on a Roller Style Garage Door, we willl need sizes to work you out a cost. Depending on what type of Roller garage door you are thinking of purchasing, we will need different information. Roller garage doors can be installed in varying positions, internally fitted to brickwork, between the brickwork or externally fitted to brickwork (reverse roll fitment). We would normally need to know your total 'Overguide Width' ie total width including guides and the Total 'Over Box' Height ie total Height including the Head Plate (as shown in above diagram). If you have a low headroom, sometimes the use of a 'mini roll' (or sometimes referred to as a 'micro roll') door is required, as the headplate required is reduced from the normal 300mm box to a 250mm box. If you are ever in any doubt with the sizes, we offer to come out and take all measurements that we require, and give you an exact cost. In our visit, we can also make suggestions as to how we can get the best size etc to suit your opening(s).