I wrote this for the late great Brian, many years ago, who understood the doorknob principle purrfectly - he would get up on his back paws, put one front paw on each side of the knob, and try desperately to turn it. No traction, though - I always wondered what would have happened if I'd taped a piece of sandpaper around it. Anyhow:
He could open any door
Put a Band-Aid on a sore
If he only had a thumb.
He could play a bass guitar
Write to a movie star
If he only had a thumb.
Shuffling cards, picking flowers
Knitting sweaters by the hour
He could climb the Eiffel Tower
If he only had a thumb.