The skill of using a straight edge to draw a line is often a challenge for young children. The examples below were used when patterns and colors where also being taught. Any straight edged shape would do, just make sure it is made of a sturdy material (cardboard works great!). The clear plastic shape that is displayed in the 1st picture was from a box of 30 purchased at a tag sale!
Mimi the Artist likes to use simple shapes to make interesting pictures. Below are examples of using a triangle pattern and tracing along its edges using either a marker or colorful crayons. Young children enjoy doing this project using crayons the painting in the spaces with paint. Water based paint was used in the pictures below: