Most kids go through a stage of being unable to tie a balloon without it farting off across the room. Water-bombs can be even worse, slippery little devils that they are.

This simple jig makes tying balloons (especially water-bombs) a lot quicker, and makes it a lot easier to build up your ammunition for April Fools.

Step 1: Materials

The jig must be smooth and snag-free, or every balloon will burst.

For this prototype, I used a dead Sharpie pen and some spare timber.

Tools included a small saw, sharp knife, drill+wood bit and a circular file.

Step 2: Cutting.

First, cut a slot in the end of the pen.

The slot needs to be wide enough to slide the neck of the balloon into, and smooth enough to avoid snagging the balloon.

I cut into the pen with the saw, twice, then smoothed off the edges by trimming with a sharp craft knife.

Then, on the side of the pen that will end up at the bottom, I cut a wide, vaguely V-shaped notch to momentarily anchor the end of the balloon during knotting.

Step 3: Drilling, Filing, Hammering.

I had a wood-bit almost as wide as the end of the pen.

I drilled a pilot hole first, then used the large bit to drill a hole for the pen to wedge into.

The hole turned out to be ever-so-slightly too small.

To make the pen fit, I used a round file to enlarge the hole slightly. Do not be tempted to hammer the pen into the hole - you will snap off the end of the pen.

Instead, grip the pen firmly with a pair of large pliers, and then hammer the pliers beside the pen.

Make sure that the V-shaped notch ends up at the bottom of the pen.

Step 4: Tying the Balloon.

Describing how to do this takes a lot longer than actually doing it. These instructions are right-handed.

Hold the end of the balloon in your left finger & thumb.

Stretch the neck of the balloon over the top of the jig, and round once.

Stretch the end of the neck over the wrapped neck, and down through the slot. Let go with your left hand.

Roll the balloon off the jig - the neck will stay in place just long enough for the end to pass through the rolling loop, completing the knot.

I made a video of the tying process - it is so short, I almost couldn't be bothered uploading it to YouTube...

Step 5: Finishing.

There you go - all done.

The important part of the jig is the actual pen. The lump of wood is just to hold it.

You might want to fix the jig into the end of a longer piece and tuck it under your armpit, or fasten the wood to the wall beside your garden tap, whichever is easiest.

As I type, a coat of waterproof stain is drying on the timber, because it is bound to get soaking wet on a regular basis. You might want to paint yours.

The jig does not have to be made from a pen - you could carve it from a section of dowel, or a piece of copper tubing. It doesn't really matter as long as it is fairly smooth to allow the balloon to come off the jig when knotting.

Let me know if you found this useful, and maybe post a picture of your own version?