Use a carpenter's level.
Chat with our AI personalities
A collar tie
Check out "horizontal cylindric segment" in Wolfram Alpha Online. That is the correct term for the solid you are looking for. Wolfram Alpha - "The solid cut from a horizontal cylinder of length L and radius R by a single plane oriented parallel to the cylinder's axis of symmetry (i.e., a portion of a horizontal cylindrical tank which is partially filled with fluid) is called a horizontal cylindrical segment."
Horizontal.
It is called a horizontal line!
Level is a palindrome that is a synonym for horizontal