This Instructional Activity is a part of the Lesson 12, Unit 1, Grade 8. In this activity, students build quadrilaterals that contain congruent sides and investigate whether or not they form congruent quadrilaterals. In addition to building an intuition for how side lengths and angle measures influence congruence, students also get an opportunity to revisit the taxonomy of quadrilaterals as they study which types of quadrilaterals they are able to build with specified side lengths. This high level view of different types of quadrilaterals is a good example of seeing and understanding mathematical structure. Watch for students who build both parallelograms and kites with the two pair of sides of different lengths. Invite them to share during the discussion.