Before installing the Quad Rail and when you are installing the low profile gas block.
Get a regular Large paperclip straighten it out all the way. Then put a 1/4 inch L shaped bend on one end of it. Insert the bend through the hole in the low profile gas block where the gas tube goes and down into the gas port hole on the barrel. Then tape the long end of the paper clip to your barrel until you are completely through doing the low profile gas block installation. This will guarantee that the gas port is not obstructed while you are working. Then remove the tape and the clip and WHALA! Gas port hole is functional.
Don't forget to removethe wire from the low profile gas block so you can insert the gas tube!