This can be used as a follow-on from Two on Five.

You have interlocking cubes of three different colours - $2$ of one colour, $3$ of another colour and $4$ of the third colour.
It could look like this;

This is slightly different from Two on Five but is seen as an extension for the highest attaining. You might like to go there first!

The nine cubes are to be connected in the usual way with the following rules being applied.

THE TWO YELLOW CUBES ARE NOT ALLOWED TO TOUCH WALL OR FLOOR SURFACES.

THE THREE BLUE CUBES MUST TOUCH ONE SURFACE ONLY THE WALL OR THE FLOOR

EACH OF THE FOUR RED CUBES MUST TOUCH BOTH WALL AND FLOOR

Here are two examples that obey the rules;

See what others you can find.
How many will there be?
At some point ask yourself "I wonder what would happen if I ...?"