Constructive Triangles: 1st Rectangular Box

A detailed guide to understanding the Constructive Triangles: 1st Rectangular Box material and how it is used within the Early Years curriculum.

How does it work?

With the Constructive Triangles, the child explores how triangles relate to and can be the building blocks of other plane figures. The 1st Rectangular Box relates various types of triangles to various types of quadrilaterals, from squares to rhombi. This material provides practice at visualizing and manipulating straight-sided figures in new ways, ones that will be applicable when the child studies equivalence and area in Elementary.

Prerequisite Skills - This material is the first of the Constructive Triangles series and, as such, does not have prerequisites. However, it is recommended that the child have some familiarity with quadrilaterals before using it: square, rectangle, parallelogram, trapezium, and rhombus.

As with all Sensorial materials, the benefits of the Constructive Triangles are best enjoyed by the child who has developed their ability to work logically through multi-step tasks. The exercises of Practical Life are the ideal training ground for this. Extensive work with Practical Life activities or other real, everyday tasks is the best way to prepare a child for this and other Sensorial activities.

Introducing the 1st Rectangular Box

sample lesson.

Start by watching this sample lesson from our Guidepost Homeschool platform that will familiarize you to the Constructive Triangles and their use.

If you are already subscribed to Guidepost Homeschool, scroll down to see all the corresponding lessons where this material is used in our curriculum. To unlock more than 2,000+ lessons subscribe to Guidepost Homeschool today.

how to set up.

Setup - Carefully remove all packaging material. Arrange the triangles in the box in the order indicated by photos shown below. This gets the triangles ready for the child's work with this material.

Usage Tips - Constructive Triangles are suitable for use either on a work rug on the floor or at a child-height table. The picture shown indicates how the activity looks in process.

Bottom Layer
Bottom Layer
Middle Layer
Middle Layer
End Result
End Result

For Guidepost Homeschool subscribers

If you are already subscribed to Guidepost Homeschool, start in the order below to navigate to the corresponding lesson plans using the Constructive Triangles in our Altitude learning platform.

Wondering about supplies used in particular lessons? Detailed materials lists can be found at the beginning of each lesson in Guidepost’s Altitude system, as well as on the materials cards at the beginning of each unit.

  • Corresponding Altitude lessons

    Lessons where the Constructive Triangles are used

    Sensorial: (3-6) No Isolated Sense

    • Introducing the 1st Rectangular Box

    Geometry: (6-12) Constructive Triangles - Explore

    • First Rectangular Box Part 1 - comparing sides and making a quadrilateral
    • First Rectangular Box Part 2 - making a parallelogram
    • First Rectangular Box Part 3 - making a rectangle
    • First Rectangular Box Part 4 - making a square
    • First Rectangular Box Part 5 - making another parallelogram
    • First Rectangular Box Part 6 - making another parallelogram
    • First Rectangular Box Part 7 - making a trapezoid
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