For Beckson Portlights
Eliminate the laborious chore of turning down each dog when you see rain coming. Cam latches are stronger than knobs or levers, and enable ports to be opened or closed with a quick flipping motion.
Cam latches are self-lubricating, non-fouling, and vibration resistant.
They provide positive closure, and the securing pressure can be fine tuned in 1/4 turn increments.
Cam latches are available to retrofit your older Beckson ports, and fit many other manufacturer's opening ports using 1/4-20 toggle bolts
The "whistle" shaped cam latches are tapped to thread onto a 1/4-20 threaded stud; cam latch assemblies add a 1/4-20 SS toggle bolt and a portlight frame pin
Both cam latches and cam latch assemblies are sold in pairs
TIP If you are replacing your original twist knobs with cam latches, you will need to know that the terminal threads on the stainless steel 1/4-20 threaded toggle are crimped to prevent the knob from accidentally being lost.
To remove the knob, you will need to reshape the crimped threads with a die, or triangular file.
Alternatively (but not as good), you can carefully unscrew the knob until very firm resistance is encountered, reverse direction until the knob spins freely, unscrew the knob again until firm resistance is met, reverse again. Keep repeating this until you have forced the knob past the crimped threads.
Work gloves will help.
More complete instructions are available from Beckson.