Gather materials: mousetrap, lightweight wood or foam board, 2 long axles, 4 wheels, string, glue, tape, scissors, drill or awl, ruler
Cut the chassis to a long, narrow shape
Mark and drill axle holes near the front and rear of the chassis
Insert the axles through the holes
Attach the wheels securely to the axle ends
Mount the mousetrap near the rear or center of the chassis
Attach a lever arm to the mousetrap snap arm
Tie one end of the string to the lever arm
Wrap the string around the drive axle
Set the mousetrap by pulling back the lever arm
Align the wheels and axles so they spin freely
Test the car on a flat surface
Adjust wheel alignment, axle position, and string length if needed
Reduce weight and friction for better performance
Secure all parts firmly before final use