I bought my kids some Ekorre hand rings from Ikea years ago. I installed them in a spare bedroom and put a mattress underneatht. It was winter so they had a ball swinging and playing on those rings.
It was great exercise and they got to a point where they could do quite a few tricks on them. The biggest problem was getting them to not stay on them too long. One kid would invent a move, and the other would want to try it immediately. You know how it goes with kids.
I recently thought about those rings because I wanted to build an old-time swing –the kind that you would tie up under a tall tree out in the country.
The rings had an ingenious system for adjusting the rope. It consisted of a 3.5″ disc with eight 1/2″ holes drilled evenly around the circumference and a small piece that is sort of coffin shaped, with a 3/4″ hole drilled on one end, and four 1/2″ holes drilled in a diamond shape.
The way they work is simple. The disc shape is positioned down near the seat of the swing. As you thread the 1/2″ rope through the holes, the friction of going in and out of the holes locks up the rope to hold the swing securely, and adjustment is very quick.
The same is true for the top piece. The larger hole is designed for a carabiner clip, so you can lock it into a large eye hook, and as you can see in the picture, I further locked the rope by threading it under one of the loops.
These two simple pieces of hardware could easily be used in the shop to tie things up, and I built the four pieces in a no time at all. After cutting the shape out on the band saw, I used a couple Forstner bits for the holes, and a roundover bit in a small router.
If you enjoy making toys out of wood, check out shopwoodworking.com for a bunch of great toy titles, many of them currently on sale.