Geoboard

http://www.mathlearningcenter.org/web-apps/geoboard/

About:

Math Learning Center (2015) writes:

Geoboard is a tool for exploring a variety of mathematical topics introduced in the elementary and middle grades. Learners stretch bands around the pegs to form line segments and polygons and make discoveries about perimeter, area, angles, congruence, fractions, and more.

For Education:

Students can use this tool to design and compare 2-Dimensional shapes. 

Breaking Barriers:

This tool can be used by students with cognitive imparements to visually represent geometric mathematics.

Required Age:

This tools is for students in grades K-12.  No age restriction exists.