all sizes and shapes of tin cans
adhesive tape for any rough edges
Ask your mother to save tin cans of different shapes. Ask her to help you be sure both top and bottom lids are off.
Tape edges with adhesive tape.
Now you are ready to build sand and block castles. Set the can on the sand. Fill it with wet sand. Then lift the can carefully, leaving the sand smoothly shaped like the inside of the can. Each can will make its own shape. A flat can will make a boat shape. A tall, round can will make a castle tower.