Ikelite 69540 Instructions Manual page 16

6. Press the port firmly towards the housing until the base of the port
is almost flush with the housing front. If there is resistance, remove
the port and re-check that the thumbscrews are loosened and the
o-ring is properly lubricated.
Small gap
~ 0.15" (4mm)
7. Tighten all three thumbscrews while holding the port firmly towards
the housing. The thumbscrews should thread in completely until
the head touches the port. If the screws are difficult to turn and/or
they bottom out before their heads are flush, it is an indication that
the port is not pushed far enough down on the housing.
16