to sump or not to sump

[BCReefer]

Pardon my ignorance but if you predrill holes for the future and then I presume you add some sort of stopper. How do you add the equipment at a latter date with out popping out the stopper and having water run out? I am in the midst of looking at getting a 50G tank with a sump etc and I am interested in this also. The above link is good help.

Thanks