One of our favorites, the Broad Stair or Brown Stair is a constant attraction in the Montessori classroom. A frequent partner to the Pink Tower, the Broad Stair shares some qualities in common with its upright partner: dimensions in diminishing tenths that support the Base-10 system and the proportions of the base of each prism. But while the Pink Tower teaches children about the relationship of size and weight, the Broad Stair teaches children to distinguish by thickness. Each prism differs in its thickness, such that placing the prisms in sequence creates an orderly staircase.
Once the stair is built, the real fun begins. Children initially develop their visual and tactile discrimination by building the simple staircase (although there's also some good gross motor control in carrying the heaviest prisms back and forth from the shelf to the mat.) After the stair is mastered, children may discover that they can align the thinnest prism in the space created between the height of each of the other stairs. Or they may grade the stair from the extremes or from the midpoint. Or they may play distance games with the superlative, positive and comparative language describing the prisms. Or they may discover some of the extensions that exist when they combine the stair and tower. There are plenty of ways to build a tower, but only these materials together do so in a way that also reinforces the Base Ten number system and expands on the child's understanding of the relationships of dimension.
Whether the stair is enjoyed by the youngest children practicing their carrying and placement on the mat or the most advanced children exploring the Grand Array, which combines all the sensorial materials at one time, the children find endless engagement in this carefully designed material.