Am going to replace a marelon thru hull and ball valve with same. Question is what is a good way to hold the thru-hull on the outside of the boat while screwing on the ball valve from the inside? Once I get the thru-hull bedded I don't want it to turn and I assume it will - it did when I was taking the ball valve off which is why I'm repalcing the thru-hull too! This is so much fun. Thanks.