This would be a line, which has no width, no thickness and no endpoints, but has infinite length.
A plane
A line fits this description.
a point
Most stone table tops and benchtops are at least 20mm thick, but they will require support for the stone along the full length and width at this thickness.
A point has no length, width, or thickness. A line has infinite length but no width or thickness. A plane has infinite length and width but no thickness.
Time has no length, width or thickness.
A line has infinite length, no width, no thickness, and no endpoints.
This would be a line, which has no width, no thickness and no endpoints, but has infinite length.
A point.
If the bar is a three dimensional object it will have some thickness. Then, assuming it is oblong in shape and knowing its length, width and thickness: Surface_area = 2 x (length x width + width x thickness + thickness x length)
Length
A plane figure
capicity=length*width*thickness
Length times width times thickness
It is Length.
Density = Mass / Volume the Volume is what you just said ... length x width x thickness