click on what, precisely?

It's easy to have too much of point-and-click games, but once in a while, as a change, they can be fun. I'm currently playing Submachine Zero: Ancient Adventure, which has much better drawings and sound than quite a few I've discovered.

Unfortunately, I'm stuck. Can anyone help? So far, I've found three red jewels and a stone, and a room with what looks like a block of stone with a pole in it, but I can't get past the second door with the sliding spikes.

I know in these games that it can be difficult to remember or describe exactly what actions lead to which results, but if anyone else would like to have a go and perhaps give me a pointer in the right direction, I'd be grateful.