Chase Crowson wrote an answer about Yakima Multimounts 1 Pair on April 19, 2009
I wouldn't do it. The straps don't grip very tight. Why it is good for kayak paddles is that there are wide paddle blades on either end that won't pass through the small 5" opening. If you had an axe with a single head on it, what would keep it from sliding on through? Perhaps you could get the straps tight enough, but would it be worth the risk of an axe flying down the Interstate if you had to apply the brakes hard?