There are various tools used during assembly of piping network in a plant. One of such tools is a Flange Alignment Tool. It is used for aligning two flanges together before bolting them tight.
These pins are safe, fast, and effective in aligning flanges. They have a tapered shaft which eliminates the need for hammering and prying when lining up flange bolt holes. They eliminate the need for hammering drift pins or fighting with spud wrenches.
Procedure
Find the best bolt hole to insert 1 bolt-hole specific pin, turn 180 degrees, then insert the second bolt-hole specific pin and turn it 180 degrees to line up any size and series of flange. To remove Flange Alignment Pins, simply rotate each pin another 180 degrees. At that point you should be able to remove each pins easily by hand.
Here is a video from youtube showing how to use these pins.