Maybe I missed this one if someone has already posted this.Saw a Brownells commercial for this product and thought it very neat. Having never mounted a gas block before, but getting ready to do one, I thought this was a cool trick. I'm sure there are other methods, but this is slick and easy.
Little plastic breakaway pins that you drop down the gas port, turn the gun over and they help you align the gas block. After tighening the gas block turn the barrel back over and break the pins out.
Brownells was out of stock so I noticed they got them from UniqueTek. But, while I was on UniqueTek's web site I noticed these are actually from HB Industries, so I direct ordered them from HB. What's not clear is whether you only get one set or several, as one picture implies four sets. Anyway, thought everyone might like to see this product.
Also comes in .30 cal size. Longer pins.
http://hbindustries.net/products/hbi-22-cal-pins/http://hbindustries.net/http://www.uniquetek.com/