4 beer openers actually.

Two can make it easier to adjust the tension cause you can just set both of them and then tighten without worrying about it.

As for tyler garrison anyone strong enough to ride a bike should be able to pull/push the wheel hard enough to get the proper chain tension. I suggest you try holding the wheel at its front and pushing rather then pulling. This way you can keep it centered alot easier as you tighten it.