The opening to which a sliding water-tight door is to be fitted in a ship should have an angle frame all round at the edges of the plate to stiffen up the plating. This angle is on the side of the plate opposite the door. The sketch shows the general construction of a sliding watertight door at the end which takes the screw for sliding the door open. A and D are the sides and top of the cast-iron frame which forms the bed for the door to slide on. B shows pieces of plate, generally about 3 in. broad, which form the back sliding surface. The door itself (C) is a, casting. Across the centre and bottom of this is a web, as well as that shown at the top. These webs are solely for stiffening the door. A hole is made through at the centre to allow the door to travel up the screw when the door is being opened. The centre of the screw is usually kept about 6 in. from the bulkhead, and it and the gearing rods are supported by cast-iron brackets. When the gearing has to be angled, bevel wheels are used about 6 in. in diameter, with thirty teeth of 3/8-in. pitch.

The gearing rods are usually about 1 3/4 in. in diameter.

Water-tight Sliding Door.