Rhem 2 help

I just finished this game and may be able to help. First of all, the clock changes every time you use it, so only hit it once. After that you must correlate the symbols on the clock to the letters on the various openings. You use the symbols at 1:00, 2:00, 3:00, 9:00, 10:00, 11:00, and 12:00. Exit and reenter in that order and the covering should stay open. FYI; MaGtRo has a great walkthrough and this answer is dealt with rather completely on (About)page 28.