The Triple Hander Threader is big. Big in that you can easily hold on to it in a roof. You can toe hook it and you can bicycle it.
The tapered design allows you to adjust its difficulty on different angles of the wall though it is best suited for roofs.
Your hand will slide down to the lowest point in a roof where the diameter of the hold is 2-1/2" inches. So pretty wide for a child but still very fun to be grabbing onto something so big.
In a vertical orientation, the taper of where you grab runs from 2" inches to 3" inches. If you flip it upside down, you can get your hand down to the 2" portion of the hold.
For a smaller, easier-to-grab version, check out the 34% smaller Double Hander Threader.