I'd presume the purpose is to make the bulb work ...?
Sometimes a weakling like me needs the plug to seal the hole then squeezes as hard and fast as I can. Then the mighty Packard worketh. Hurray.
Other times clumsy person like me removes plug and covers hole with thumb and squeezes carefully to get the shutter to open Only and stay open for focus or long shutter speeds. Opps. I forgot, just at the right moment uncover the hole to maintain openness.
Later leave hole open while squeezing all air out, cover hole and maybe the Packard will close.
I do have problems with this occasionally.
Not kidding.
Tin Can
Uh oh. You didn't accidentally order from Pack Hard Adult Toys did you?
Okay, to be serious - my Packard bulb is different. Same shape, same expressed ring in the middle, but one end has an embedded brass nipple for the hose and the other end a small hole to cover with your finger. No plug at all. HOWEVER, I always use it with my finger over the hole. Maybe Packard finally wised up.
I hope we can figure this out.
.
The hole is there so you can open the shutter and leave it open (to focus lens or long multi second exposure.) The plug is there for when you do the fast exposure.
Kent in SD
In contento ed allegria
Notte e di vogliam passar!
OP is most likely not using it on Packard but a Century IBT which can actuated with bulb with or without the evil hole and plug.
Tin Can
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