Determine how long you want your balloon chain to be. For each foot, you will need one balloon and 14 inches of monofilament wire, plus an extra 10 feet to secure the wire.
Determine where you want your balloon chain to originate. Ensure there are no trees, telephone or electrical wires or other obstructions in the way. The middle of a largely unpopulated area, like a large park, field or festival location is best.
Pull two feet of monofilament wire free from its container. Run an extra three feet along the ground. Stack the cinder blocks on top of the monofilament wire that's on the ground. Put three cinder blocks directly on top of the monofilament wire. Place the remaining three cinder blocks on top of the already placed three cinder blocks. Ensure the blocks are even and are holding the wire securely.
Extend the monofilament wire around the outside edge of the cinder blocks. Tie the free end of the monofilament wire around the excess monofilament wire in a square knot the best you can, centering the knot over the center of your pile of cinder blocks. You won't be able to tie a true square knot since one of the monofilament wire is not loose.
Fill your first balloon with helium. Tie a knot in the bottom of the balloon. Wrap the monofilament wire three times around the tied end of the balloon, just above the knot. Ensure you use the monofilament wire that is still connected to the container, not the loose end.
Extend the balloon about one foot into the air. Fill a second balloon with helium. Tie a knot in the bottom of the balloon. Wrap the monofilament wire three times around the tied end of the balloon, just above the knot.
Repeat Step 5 and Step 6 until you have reached the final balloon and foot of monofilament wire. When you wrap the final piece of monofilament wire around the final balloon, tie the final end of the monofilament wire in a square knot the best you can around the knotted end of the balloon.