This is certainly a magic item that is open to many possible interpretation. Here's my take on it.

heirodule said:

I guess the window works the same way. Right?

I'd say so. The pit must be placed on a horizontal surface while the window must be placed on a vertical surface. That's how they are distinguished from each other.

heirodule said:

On what thickness wall? [it says 2 feet deep, so I know this]

Yup.

heirodule said:

Can you put on into an adamantite wall?

There's nothing that limits the materials of the wall's construction in the item description so I'd say so.

heirodule said:

What if you put a pit on a 2 foot thick floor?

It'd simply create a hole through the floor. If the floor below is less than 10 feet below the level of the floor onto which you first place the pit I'd say that the magic involved continues downwards until a depth of ten feet has been reached. So in effect, the pit might create two holes in two floors of a building if they were only eight feet apart from each other.

heirodule said:

What if you put a pit on some important item?

A pit must be laid on any horizontal surface large enough to contain it; that is, anything that extends beyond 10 feet in width and length on the horizontal plane and otherwise able to act as a stable base onto which to anchor the pit. Note that creatures, even if large enough to meet the size requirements, are not surfaces and so cannot anchor pits upon their bodies.

heirodule said:

Can you put a pit on a section of floor where someone or and object is standing?

Before it is placed on the ground the "pit" is actually a fabric patch removed from the robe. It cannot be settled onto the ground properly if there is something covering the ground, such as an object or creature.

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