Is there, or has there ever been, a unambiguous word for "the leftmost extreme" or "the rightmost extreme"? Such words exist for the other two dimensions.

Imagine you are floating in a cube in space.

• You can go up until you hit the top.
• You can go down until you hit the bottom.
• You can go forward until you hit the front.
• You can go backward until you hit the (back/rear).
• You can go left until you hit the _______?
• You can go right until you hit the _______?

Is there, or has there ever been, an unambiguous word for "the leftmost extreme" or "the rightmost extreme"? Such words exist for the other two dimensions.

Imagine you are floating in a cube in space.

• You can go up until you hit the top.
• You can go down until you hit the bottom.
• You can go forward until you hit the front.
• You can go backward until you hit the (back/rear).
• You can go left until you hit the _______?
• You can go right until you hit the _______?