Dumb question... But necessary

whats the other end look like?

There is no attachments or welds on the bottom but i did find written message to a "Wayne" to put 2 holes in the tank. I banged on the tank and heard the wa wa wong sound as suggested in earlier in the thread, and when i put on its side and rolled it i heard a rustling sound from its contents. Im busy Friday working and taking a load of short steel and car batteries to the yard, but will have time on Saturday to work on it. Should i try to connect a air hose to the valve to check for pressure? Or should i try to open the plug on the other side? Thank you.