Review on Oatey 33403 4-Inch Plastic Plug with Galvanized Screw and Wing Nut by Rick Kreutzer

Yes, that's right, love. You've got a 4" PVC hole and you're tired of dealing with screw caps that get stuck over time (or worse, the folks who made the holes were a bit beveled and have bits of quick setting material or other debris left in the threads, problems guaranteed). Opening and closing the lid for cleaning. Here is your answer. Virtually airtight when fully closed but light enough to open again when you need access. I am sure that it is not suitable for print use. But if you have pipes, you also need access - they're way better than most other cleaning caps.