Older child builds or creates something. Younger sibling may add exactly one element, and the older child decides what that element is: 'You can put one block on top.' or 'You can draw one cloud in the sky.' The older child retains authorship and approval authority; the younger child has a real, chosen contribution. The one-element rule prevents the destruction that usually follows when younger siblings gain uncontrolled access to an older child's creation.

What you need

Whatever the older child is already building or drawing

How to do it

1The instant the younger child reaches for the older's creation, say it as a right, not a question: "You can add one thing. [Name], what can they add?"
2Older child specifies exactly: put one block here, draw one star there. No room for interpretation.
3Younger child adds that one thing. Nothing else.
4Older child decides whether to offer another round. The choice stays with them.

Variations

If the older one refuses to allow any addition: accept it once, no pushback — 'not today' is a valid answer, and forcing it teaches the opposite of what this card is for.
How it ends: once the one thing is added, the younger child steps back on their own — the rule doing the work means you don't have to enforce the exit.
This one prevents the invasion moment from becoming a fight. If it's already a fight, use The Separate Reset (B006-20) instead.

💡 Parent tip

The difference is a statement versus a question — 'Can [name] add something?' gives the older child an easy no. Stating it as a right is what eliminates most of the resulting conflict.

What your child develops

Authorship with contribution — younger child participates without threatening the older's creative control
Permission-granting — older child practices the agency of deciding what access to grant
Impulse regulation — younger child practices executing a constrained contribution rather than taking over