Asked on the landing

Richard James, a mechanical engineer, discovered it in 1943 when a tension spring fell from a shelf and kept moving. His wife Betty named it, and the first Slinkys went on sale in Philadelphia in 1945.

Lift the top rings onto the step below. Gravity pulls that end down while the rest of the coil follows, so the energy passes along the spring as a wave and it flips end over end, step after step.

Metal is the original: heavier, louder and the best walker on stairs. Plastic is lighter, quieter, more colourful and better at surviving a drop, which is why many families start younger children on plastic.

The Classic is 2.75 inches in diameter. Slinky Jr. is about 1.5 inches, the Giant metal Slinky about 3.5 inches, the Giant plastic coils about 5 inches and the Extreme Rainbow 9 inches tall.

Find the end, hold the coil loosely and turn the tangled section the opposite way to the kink, one ring at a time. Never pull the two ends apart — that stretches the wire. Our guide walks through it step by step.

Metal and plastic Slinkys are recommended from 5 years. Slinky Dog pull toys and the plush start at 18 months, the wind-up at 3 years and the Slinky Challenge Game at 8.