Examine the Door

Sam took a closer look at the first door he tried to open. The door was part of larger wood column, intricately carved. Upon closer examination he noticed that, unsurprisingly, many of the carvings were sexual in some way or another. An intricately carved pair of tits here, an etching of a woman going down on another woman there. Very dirty. Very on brand for camp.

After looking for awhile, he noticed one shape that was decidedly simple and not remotely sexual. It was just a circle. It was hard to see because the line was integrated into some of the other etchings in some spots, but it was definitely there.

So now that he'd found something suspicious, he had to figure out what to do. He had to use "all the tools" to "put his key in the right hole." The question was...