What is a general word for a shape which allows entry/exit through only one of its faces? [closed]

What is a general word for a shape which has only one entry/exit side or face?

For example, if it's a rectangle with 4 sides, then things can only pass in/out from one its side while other sides are blocked.

The field of context is mathematics, computation, physics.

I think possibly you were "being creative" when you wrote...

For example, if it's a rectangle with 4 sides, then things can only pass in/out from one its side while other sides are blocked.

Consider:

Physicists often get stuck with boring names for their work, Carroll said, and in the case of quarks, they needed to distinguish their characteristics. So they got creative, he said. Gell-Mann and George Zweig gave them “flavors” to describe their spin and electric charge — up, down and strange. Later physicists added the flavor “charm” to the mix, and quarks were further designated by the colors blue, green and red, even though the particles have no visible colors.

PBS.com

In other words, physicists (and sometimes mathematicians) often use "colorful", "visual", and "flavorful" language to describe aspects of functions.

Possibly this belongs on Math.SE, but I would like to suggest ...

Dimensional/ shape/color/side SORTER

Based on the (mal)appropriation of the name of the child's toy.

I think this goes one dimension more than what you asked, and is more discrete. i.e. It permits entry on one side only; moreover, it selects by shape, and sometimes by color.

Optimum performance of entrance in such a container requires an outside intelligence such as a child, and can be measured statistically. Exit is determined by random chance of a chaotic shaking...statistically a zero.