Our bar, like many others, is cold rolled steel. However, our bar is milled and then hand-straightened before assembly. Our bar tightening system forces this machined edge against the side of the miter slot and also allows you to reference off the bar if necessary. We feel our adjustment plugs are better then multiple cutouts in the face of the bar, which can cause flexing, because of sacrificed strength. And, since the bar is seated against the miter slot, which should be parallel to the saw blade, everything will work correctly.
Some gauges have adjustment washers on both sides of the bar.
The theory being that as they are tightened the bar will automatically be centered in the slot. This assumes the washers expand evenly and do not cause the bar to track through the miter slot at an angle. Although our bar tightening system cannot be adjusted from the top, our plug method provides a stronger, truer running bar. And since we use a longwearing self-lubricating material for our plugs, adjustment is seldom needed. Simple one-step indexing for common angles has always been the hallmark of our miter gauge.