Hello everyone, many times I have needed to mark a square line on the web of a beam to attach a connecting plate or angle, or to layout a set of holes. On smaller beams a machinists square can be used for this purpose with relative ease. First set the blade of the square flush with the surface of the head, then lay the blade of the square against the inside of the flange of the beam with the square head laying on the surface of the web of the beam, line the edge of the square head up with your distance layout mark and draw a line along the edge of the square head. You will now have a line that is perpendicular to the flange of the beam. If you need this line to be longer and if the size of the beam permits, go to the flange opposite the one that you used to draw the first line and lay the blade against the inside of this flange and line the square head up with the end of your first line and continue the line across the web. This method works pretty well on beams that are in the W6x#whatever to the W10x#whatever range. One limiting factor for this method would be the size of the inside radius of the beam, if this radius is too large you will have a more difficult time getting an accurate square line. For larger beams I have seen people shear out a piece of 10 or 12GA. sheetmetal that is either a square or rectangle, taking care to be sure that all the sides are of equal length and the corners are all square. Then they stitch weld a piece of pipe to one of the edges, being careful to make sure that the pipe is also square relative to the other edges. This can then be layed into the inside of the beam with the pipe being pushed up against the inside of the flange and the edge of the tool can be used to draw the square line layout. Another method that I have seen used, starts with a similar piece of sheet metal as the one above but instead of attaching a piece of pipe to one of the edges they will instead make two 90 degree bends that are about 3/4" of an inch apart from one another and bent in opposite directions. When you place this against the inside flange of the beam, it allows the edge of the tool to clear the inside radius of the beam and have the rest of the tool lay flat on the web so that you can draw the square line along it's edge. I know that there are other methods to achieve this sort of thing and I hope some of you other folks will take the time to post them. Regards, aevald