Drain on whirlpool tub

Can some one tell me what this is. I have never seen one of these before.


most likely contains a cable that connect to the drain plug.

on the other end should be the flapper you use to open and close the drain.

Now that make perfect since, thanks for the help

Looks like a sawn through I-joist from here.

yeah, and right above a tub that’s bound to get quite heavy.

at least it’s more toward the front and not through the middle of the tub.

would have made way more sense to notch through the OSB instead of the top of the joist.