Drawing a 3D rectangle is a stepping stone in the process of learning to create three dimensional drawings from two dimensional beginnings. You can practice 3D rectangles by hand or using digital art software on your computer. When teaching an art, math or computer course, it is often beneficial to start your students off drawing 3D rectangles and squares as well as other geometric forms including prisms, cubes, pyramids and cylinders by hand. Following their mastery of three dimensions by hand, allow students to learn and practice the same creation process digitally using art software.
Lightly draw a cross -- a lower case "t" shape, (a vertical and a horizontal line) -- in the center of your paper with a pencil. This is your temporary guide, which you will erase later.
Draw a 1 inch by 1 inch square using the guide to create a perfect square with 90 degree angles in each corner.
Draw a line starting at the top right corner of your square and extending 2 inches at a 45 degree angle. Draw a line starting at the top left corner of your square and extending 2 inches at a 45 degree angle. These two lines will be diagonal against your guide horizontal line, and parallel to each other.
Draw a line to connect the ends of the diagonal 2 inch lines with each other. Then draw a 1 inch line starting at the most right 2 inch diagonal end straight down perpendicular to the horizontal line from your guide.
Draw a line connecting the bottom left corner of the square to the last 1 inch line end you drew in Step 4. Now you have a 3D rectangular geometric box. Carefully erase your guide lines.
Open up a computer program, free software like Paint or more complex art software, and repeat steps 1 through 5 in the digital art program.
You can add color, shading or shadows to your 3D rectangle to make it more realistic. Or, you can complete the back square and connect it to the front -- as used in mathematics geometry drawing practice.