Lesson objective: Identify and differentiate between parallel and perpendicular lines.

This lesson helps to build procedural skills with identifying parallel and perpendicular lines. A square corner is used here to identify right angles because it highlights the perpendicular lines. This work develops students' understanding that parallel lines must remain an equal distance apart and perpendicular lines intersect to create right angles.

Students engage in Mathematical Practice 6 (attend to precision) as they extend and closely examine lines to determine if they are parallel or perpendicular. Students use square corners to identify right angles of intersecting lines, as well as determining if lines are an equal distance apart.

**Key vocabulary:**

- intersecting lines
- parallel lines
- perpendicular lines

**Special materials needed:**

- sheet of paper for checking right angles (optional)