But less delicacy is needed for this tip: use a laser level! See, it's like carpentry, you can explain. We need things plumb and square.
Simply set up the level on a stool or other item of appropriate height, stand next to it, and turn slowly as your cooperative partner inserts pins (or makes marks) on the bright shiny line.
I want you to know I don't think only men can or do use tools. Of course a female helper can make great use of this tip, too. It just seems that they are often in short supply when hemming time rolls around.