Ikelite 6973.10 Instruction Manual page 12

3. Apply a very thin, even layer of lubricant to the exposed portion of
the front o-ring and to the lens port sealing surface. Avoid dry spots
or uneven build-up of lubricant.
4. Loosen the port thumbscrews until they do not show on the inside
of the lens port.
5. If using a port with a dome shade, align the port so that the tall
projections on the dome shade are in the 12 and 6 o'clock
positions.
Shade
Thumbscrew
Zoom gear
O-ring
Thumbscrew
groove
12