A ninja line is a strap you tension between two trees, with monkey bars, rings and knotted ropes clipped along it so kids can swing hand to hand across the garden. A good kit for kids states an age range and a weight limit, comes with clear tree and height rules, and lets you move the obstacles around as they get stronger. Set it low enough that their feet are close to the ground, and supervise every session.
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Quick picks: the Slackers NinjaLine 36 ft Intro Kit for a first line, the Slackers NinjaLine Pro Kit for more obstacle variety, and the Trelines Ninja Warrior Obstacle Course as an alternative with a stated tree spacing.
Why a Ninja Line Suits Young Traceurs
Hanging and swinging build the grip and upper-body strength that parkour moves like cat leaps and bar swings depend on. For children, it’s also simply good play. The CDC recommends that children aged 6 to 17 do muscle-strengthening activity, such as climbing, on at least 3 days a week. Our guide to bar movements in parkour shows where this kind of swinging leads later on.
What to Look For
- A stated age range and weight limit. Kits on this list are rated from ages 5 or 6, with weight limits between about 220 lb and 250 lb.
- Clear tree requirements. You need two healthy, solid trees. Slackers recommends trees of about 12 inches in diameter.
- A ratchet tensioner. It lets an adult tighten the line properly and release it for storage.
- Movable obstacles. Clip-on monkey bars, rings and knotted ropes can be spaced closer together for small children and further apart as they improve.
- A storage bag. Straps last longer when they’re not left out in the weather.
Three Kits Worth Considering
We haven’t tested these ourselves. The details come from each brand’s own page or manual, or from the publication named, and prices change, so check the listing before you buy.
Slackers NinjaLine 36 ft Intro Kit
- Who it suits: a family setting up a first line.
- What’s in it: according to The Toy Insider, a 36 ft line with seven obstacles: three knotted monkey fists, two monkey bar holds and two gymnastics rings, plus a steel ratchet and a drawstring bag. It lists the kit for ages 6 and up and a 250 lb weight limit.
- The catch: seven obstacles is a starter set, so confident kids may want add-ons.
Slackers NinjaLine Pro Kit
- Who it suits: older kids who want harder grips than bars and rings.
- What’s in it: the Slackers Pro Kit manual lists two pipe holds, three ball holds and two cone holds, with room for up to 12 obstacles on the line. It’s rated for ages 5 and up, with a 250 lb maximum user weight.
- The catch: ball and cone grips are harder to hold than bars, which is the point, but younger children may find them frustrating at first.
Trelines Ninja Warrior Obstacle Course ($100 and up)
- Who it suits: families who want a mix of bars, rings and tree holds in one box.
- What’s in it: the product page on Hape’s site lists a 36 ft line with a ratchet and eight accessories: two monkey bars, two tree holds, two monkey fists and two gym rings. It’s rated for ages 5 and up, with a 100 kg (about 220 lb) limit, and is listed at $149.99.
- The catch: it needs two healthy trees about 15 to 30 ft apart, so measure your garden first.
How to Set It Up Safely
The Slackers Pro Kit manual sets out rules that are worth following for any ninja line:
- Pick healthy trees. Slackers recommends trees about 12 inches in diameter, and warns against any tree that’s diseased or damaged.
- Keep it away from water. The manual says to set up away from pools, ponds, streams and rivers.
- Set the height for the shortest child. Measure their reach with arms up, then add about 24 inches to get the starting height of the line. When they hang from the lowest obstacle, their feet should be no more than about 12 inches off the ground.
- Test it before anyone uses it. The manual makes a load test mandatory: hang a 250 lb weight or person about 5 ft from each end.
- Supervise every session. Slackers requires adult supervision at all times, one person on the line at a time, daylight use only, and no use when the line is wet or in rain or lightning.
- Put something soft underneath. Grass is a start. A folding mat helps more, as our crash mats guide explains.
What to Check Before You Buy
- That you have two suitable trees, at the spacing the kit needs.
- The age range and weight limit on the listing.
- Exactly which obstacles are included, since some listings show add-ons in the photos.
- That the listing is sold by Amazon or the brand’s own store.
Frequently Asked Questions
What age is a ninja line for?
The kits here are rated from 5 or 6 years old. Younger children can still enjoy the lowest obstacles with an adult holding them, but follow the manufacturer’s age guidance.
Can adults use a ninja line?
Within the weight limit, yes. The Slackers kits here list 250 lb and the Trelines kit lists 100 kg. Set the height for the adult, and lower it again before the kids use it.
What if I don’t have trees?
Slackers says its line can go between posts, but only if each end can handle at least 2,500 lb. That usually means properly concreted posts, which is a bigger project than a tree setup.
Where to Go Next
For more gift ideas by age, see Parkour Gift Ideas for Kids and Teens. For age guidance, read What Age Can Kids Start Parkour?