Each group needs:

• a model room (in advance, the teacher uses heavy construction paper, cardstock or cardboard, tape and/or glue to construct; see details in the Procedure > Before the Activity section)
• LEGO MINDSTORMS NXT robot, such as the NXT Base Set (5003402) for $159.98 at https://shop.education.lego.com/legoed/en-US/catalog/product.jsp?productId=5003402&   isSimpleSearch=false&ProductLine=NXT (LEGO NXT robot constructed with 1 ultrasonic sensor pointed forward and 1 ultrasonic sensor pointed to the left side of the robot, equipped with a program for wall-measuring; see details in the Procedure > Before the Activity section)
• LEGO MINDSTORMS Education NXT Software 2.1, available as a single license (2000080) for $39.97 or a site license (5003413) for $271.96 at https://shop.education.lego.com/legoed/en-US/catalog/product.jsp?productId=prod120017&isSimpleSearch=false&ProductLine=LEGO+MINDSTORMS+Education+NXT
• computer, loaded with NXT 2.1 software
• 1 ruler
• Mapping Perimeter! Worksheet, one per student