wood is too bulky and heavy......
And rubber has a tacky texture to prevent sliding also.
Donny ... if this piece of wood weighs even 1 pound, I'll EAT it ! ...

... I just lay it in the bottom of the KB bag ... in fact, I've even thought about attaching it to the KB with industrial velcro, but I'll try the door stop first ...
But you're right about the rubber door stop ...