Key Stage 1 design and technology · Technical knowledge

KS1 design and technology: levers and sliders

A mechanism is a set of parts that work together to make something move. In Years 1 and 2, children are taught to explore and use mechanisms in their products, and the National Curriculum gives levers, sliders, and wheels and axles as examples. Levers and sliders are the usual starting point, because children can make them from card and see exactly how they work, in moving pictures, pop-up cards and simple toys.

Levers and sliders, explained

A lever is a strip that turns around a fixed point. That fixed point is called the pivot, and in a card model it is usually a split pin pushed through a hole. When you push or pull one end of the strip, the other end swings in an arc. If the pivot is in the middle, pushing one end down makes the other end go up, like a see-saw. Children can use this to make a bird flap its wing, a person wave an arm or a crocodile open its mouth.

A slider moves in a straight line, backwards and forwards, along a track. In a card picture, a strip of card slides between two guides, under small card bridges, or through slots cut in the page. A sliding strip can make a car drive along a road, a face appear in a window or a boat cross a river. The guides keep the movement in a straight line, and without them the strip wobbles off course. Cutting a slot in the middle of a page is fiddly and often needs a sharp blade, so an adult usually does it or the slots are cut in advance.

Children are taught to explore mechanisms first by playing with them, for example by trying a pop-up book and working out what moves and how. They then design their own, test it and fix problems. The curriculum says they should use mechanisms in their products, and the same design cycle applies: decide what should move, choose a mechanism, make a mock-up, try it and change it. Children at this age are not expected to know the physics of forces, only that the type of movement depends on the mechanism.

Teachers describe movement with words such as push, pull, turn, slide, up, down and across. Children may also use the words “input” (what you do) and “output” (what moves). Wheels and axles, the other example the curriculum gives, are often taught in a separate unit, such as making a vehicle. Schools choose which mechanisms to teach and when, and the understanding of movement children build now is used again in Key Stage 2 with linkages, cams, gears and pulleys.

Words your child will hear

Mechanism: A set of parts that work together to make something move.
Lever: A strip that turns around a fixed point to make something move.
Pivot: The fixed point a lever turns around, such as a split pin.
Slider: A part that moves backwards and forwards in a straight line.
Guide: A strip or slot that keeps a slider moving along its track.
Push and pull: The actions that make a mechanism work.
Split pin: A small metal fastener with two legs that open out flat, often used as a pivot in card models.

What the National Curriculum says

The programme of study for Key Stage 1 says:

When designing and making, pupils should be taught to explore and use mechanisms [for example, levers, sliders, wheels and axles] in their products
When designing and making, pupils should be taught to select from and use a range of tools and equipment to perform practical tasks [for example, cutting, shaping, joining and finishing]

Objectives from the National Curriculum in England, © Crown copyright, used under the Open Government Licence v3.0.

Try it: a moving picture of a car on a road

A child wants a car in a card picture to drive from one side to the other. Which mechanism do they use, and how do they build it?

Decide what must move and how. The car must go along the road in a straight line, backwards and forwards. That is a slider, not a lever.
Make the slider strip. Cut a long strip of card, wider than the car is tall. Draw the car at one end, and leave a tab at the other end to hold when sliding.
Make the track. Stick two thin card guides along the road, one above and one below the strip, with a gap just wider than the strip. Then tape a small card bridge across both guides near each end, so the strip can slide underneath but cannot lift off.
```
 ============ guide ============
 [car]========= strip ==========[tab]
 ============ guide ============
       ^ bridge        ^ bridge
```
Test it. Push and pull the tab. If the strip sticks, make the gap wider. If it wobbles up and down, make the gap narrower.
Compare with a lever. If the child instead wanted the driver to wave, they would fix a card arm to the picture with a split pin as a pivot, and the arm would turn, not slide.

A slider is the right mechanism for straight-line movement, with guides keeping the strip on track. A strong answer says why: “I used a slider because the car goes straight, and a lever would swing it in a curve.”

Common mistakes and how to help

Pivot pinned too tightly, so the lever will not move

Children push the split pin in firmly to make it secure, and then the card cannot turn.

What helps: Open the pin’s legs flat but not hard against the card, and make the hole slightly bigger than the pin. Test the turn before decorating.

Expecting a lever to move in a straight line

A child pushes one end across and expects the other end to follow the same line. But a lever turns, so the end moves in an arc.

What helps: Let your child push a lever strip and trace where the end goes. Then try a slider, and compare the two paths.

Not leaving enough room for the slider to move

When children draw and cut the track, they match the strip’s width exactly, so it jams.

What helps: Leave a small gap, and test with scrap card first. A slider needs room to move but not so much that it wobbles.

Pushing the wrong way and thinking it is broken

With a lever, pushing one end down makes the other go up, which is the opposite of what a child expects.

What helps: Say that opposite movement is normal when the pivot is between the two ends. Try moving the pivot nearer one end: the ends still move opposite ways, but the short end moves less than the long end.

How to help at home

Explore a pop-up book or card. Look at a pop-up book or card and ask what moves and how. Slide the tabs and pull the levers gently, and talk about whether each one turns or slides.
Make a lever from card. Make a hole in a strip of card and a backing sheet (you can push a pencil through into a lump of modelling clay), then join them with a split pin as a pivot. Draw a face or an animal, and see how the strip turns when you push one end. Keep split pins away from babies and toddlers.
Try a slider with guides. Tape two thin strips of card to a sheet with a gap between them, then tape a small card bridge across the gap near each end. Slide a card strip along the track and under the bridges, and ask your child to decide what the slider should move.
Hunt for sliders and levers. Look around the house for things that slide, such as drawers, curtains on a rail or zips, and things that turn around a pivot, such as door handles and scissors. Ask which kind of movement each one uses.

Leads on to

Key Stage 2: Strengthening and reinforcing structures
Key Stage 2: Gears and pulleys
Key Stage 2: Cams, levers and linkages
Key Stage 2: Series circuits in products
Key Stage 2: Programming and controlling products