Here is a simple example of a lever operating a little tipper that a six year old can build (with a little help of course!).

The chassis is 12 cm long and is formed using two 12cm lengths of wood and two card rectangles 12cm x 3cm.

The wheel units are rubber tap washers fitted to 5mm diameter paper sticks or dowels revolving in short lengths of artstraw.
All wood is 10mm square.
The box is A6 copycard, scored 4cm from one end and 3cm from each long side. (We pre-score the card for younger children). The hinges, shown green, are also copycard. The main lever (brown) is much stiffer. The small rectangle of card glued to the end of the box acts as a stop and prevents the lever from slipping past the end of the box.
LAMINATING - The lever will keep straightening as it is used - however, if you make two identical levers and glue one inside the other (while still folded to a right angle) you will have a lever that wants to stay bent!