The Montessori brown stair lesson, also called the broad stair or prism lesson, consists of a series of 10 wooden rectangles or prisms that are all the same length but of progressively larger heights and widths. When arranged correctly, they make a wooden stairway that appears to have an extremely broad top step and then narrower and narrower steps toward the bottom. The brown stair is part of a Montessori lesson series designed to help children draw comparisons in size and dimension.The hardwood prisms are crafted in precise progressions from 1 x 1 x 20 cm (thin) to 10 x 10 x 20 cm (thick) the consequence of disorder, and helps to improve coordination, concentration, independence, and problem solving skills through observation.