Only if you have sharp eyes, (and I mean very sharp. Best is to measure, but you don't need to shell out for a $50.00 tool. If the Hanger is square, then the Rd is vertical. Therefore is follows that the lower pulley is directly under the upper pulley, which is centered below the sprocket, who's bottom is centered below the top. That means you can determine precisely whether the hanger is square by measuring as I described in an earlier post here.

I assume you can find a straight edge and small ruler easily enough. A friend would also be handy but you can do the job solo if you don't have one.