Are you tired of splinters? Yea, me too!
I sure wish there was a way to get my pull-ups done without all those bits of wood all in my hands.

My friend, today is your lucky day!
 

A TPU grip for a pullup-bar! Not the bar - just the grip, you silly goose.

This one is designed to have a snug fit on a Ø33mm wooden rod, but i imagine it can be scaled rather well.
You could try to fit it on another size stick that you found in the woods, but im just telling ya.. its not gonna be great.

It features a criss-cross design for better grip. 

Be sure to print this in TPU for a soft and non-slippery grip.
It is sized to fit the hand of an adult. (See picture for adult and/or gripsize)