Geometric Shape Visualization Puzzle

This is an object I made as an answer key for a teacher who gives their students the following visualization assignment:

Can you visualize a solid dimensional object that can completely fill AND pass through three
different holes, a square, a triangle, and a circle? The same object
must be used to pass through all three and cannot have any moving parts. The diameter of the circle and square and the base and height of the triangle are all the same length (e.g. circle diameter = 1.0 units, square diameter = 1.0 units, triangle base = 1.0 unit, triangle height = 1.0 unit)