×Trapping the guard in that room isn't what you want to do. As you've noticed, it isn't even possible.
There's three ways to do this, listed from easiest to hardest:
Click here to view the secret text
×Trigger the power token, go around the small two-orbs room (start on the left), go around the middle part counterclockwise. Once you're next to the pressure plate, head back to the orb room.
If you do this right then he'll be to the northwest of the pressure plate while you're standing right next to one of the two orbs (on the yellow door). Trigger the orb and he'll resort to roach-like movements and aim for the pressure plate, freeing you.
Click here to view the secret text
×Get him somewhere on the right side and use the tunnel to warp to the left. This seems to require some very exact timing.
Click here to view the secret text
×Get him to cut the right gel and have the gel babies trap him. You'll then have to deal with the guard and a set of gel babies at the same time.
I can upload a demo using method 3 if you'd like but the demos on CaravelNet look much easier than mine.
