Frame glued in place, plug loose. Instructions have one glue the plug in place, first, leaving space for the frame; then, glue the frame in. I found this too awkward, as the ABS was so flexible. Trying to hold the plug in place, keeping a gap for the frame...just thought it too was to easy to end up with a misshaped tank. Drizzled thin 30min epoxy between the ABS and plug, spread it well, including between the frame and plug.