How to Make a Medieval Toy Catapult

Drill holes at the bottom of four of the rulers large enough for the carriage bolts to fit through. Put carriage bolts through the holes of two of the rulers and hold them in place with a nut on the other side. Put the carriage bolts through the air holes in the brick--one through the hole at the front and one through the hole at the back.

Lay the brick on its side so the ends of the carriage bolts are sticking up through the brick. Twist two more bolts on and keep twisting them until them are just inside the brick's air holes. Put the bolts through the holes of two more rulers so that each bolt holds two rulers, one on each side of the brick and hold in place with another nut on the outside of the ruler.

Stand the brick up again and stand a ruler up vertically, pulling it up so that the carriage bolt inside the air hole is tight against the brick. Drill a hole through the ruler just as it comes up over the level of the brick. Do the same with the ruler on the other side of the brick and put a carriage bolt through the two holes, securing it with nuts on each side so that the rulers stand up vertically on their own.

Hold the other two rulers diagonally to make right-angle triangles with the vertical rulers. Align their ends and drill a hole through each ruler. Put a carriage bolt though the holes and secure it in place with nuts. Drill holes through the diagonal rulers just as they come up over the level of the brick and secure in place with a further carriage bolt. You should have two right-angle triangles firmly held in place on opposite sides of the bricks.

Drill a hole 5/8 of an inch across int the vertical rulers, 2 inches above the level of the brick. Tie one end of the string around the middle of a carriage bolt and tie the other end of the string to the piece of wire. Thread the string through the holes you have just drilled, in through one side of the catapult and out through the other, pulling it tight so the carriage bolt comes tight against the outside of the vertical ruler.

Lay the final ruler flat on top of the string with three inches on one side of the string and nine on the other. Press a carriage bolt across the hole that the string is come out of, with the string passing under it. Go around the carriage bolt with the string and back through the hole so the bolt is held in place in a loop of string.

Thread the string under the loose ruler and back out through the first hole, take it round the carriage bolt and back through the hole, this time going over the top of the loose ruler then out through the hole on the other side. Again go round the carriage bolt, back through the hole and over the top of the ruler. Continue doing this, going twice over the ruler then then twice under until no more string can fit through the holes.

Tie the loose end of the string to a carriage bolt. Pull the long end of the ruler you have wrapped in string back flat against the brick and tie it in place. Twist both the carriage bolts which are wrapped in string in the opposite direction from the direction you just turned the ruler. Keep doing this till they pulled as tight as they can sensibly go.

Lay a mash mallow on the tip of the tied-back ruler. Hold the ruler in place and carefully undo the string that keeps it held down. Aim and let go!