Describe the process you would use to create the perpendicular bisector to a segment ab using only an unmarked straightedge and an unmarked compass

I'd open the compass about an inch (but the width doesn't matter as long as it's consistent), place the pin end on one edge of AB and use the pencil end to trace an arc above the line but about where the perpendicular bisector would come out to. I do the same from the other end of the segment, making sure the lines cross. Where they cross, I trace a straight line down to what should be the center of the line segment. I've crafted a perpendicular bisector!

Does this help you at all?