1. The problem asks to describe the locus of points inside rectangle PQRS that are equidistant from sides PQ and RS. 2. Recall that the locus of points equidistant from two parallel lines is the line exactly halfway between them. 3. In rectangle PQRS, sides PQ and RS are opposite and parallel. 4. The midpoint of PQ and the midpoint of RS lie on the line equidistant from both sides. 5. Therefore, the locus is the line segment connecting the midpoints of PQ and RS. 6. This line runs horizontally through the center of the rectangle, dividing it into two equal parts. Final answer: A line between the midpoints of PQ and RS.