Linear Flooring
The floor function [a] denotes the greatest integer less than or equal to a. For x and y strictly between 0 and 1, the probability of [2x]+[2y] being 1 is 1/2.
Line Stitching
Consider all 1 unit long line segments that have an end point on the line y=0 and the other on x=0.
Number Line Mirrors
Starting with some points on a number line, if we put a mirror somewhere on the number line, it will reflect all existing points in itself so that the resulting set of points are symmetrical around it.