If I'm using this tool to see if a bracelet measuring 7 1/2 inches will fit a 7 inch wrist, should the bracelet sit at the 7 1/2 mark or 7 mark?

The bracelet should sit at the 7 1/4" mark so as to allow for muscle movement for a 7" wrist. Don't worry about the LENGTH of the bracelet! That's why rulers don't work when measuring bracelets. The bigger the beads, the further the wire is from the wrist. It's only the circumference that matters. The 7" mark represents a 7" wrist. So you need to add a little breathing room. That's why I recommend 7 1/4". The type of clasp will also affect circumference. So you need to experiment to see what works best for your own jewelry style. For more info, visit my website. There are complete instructions with the EZ Bracelet packaging. But I get into more detail on my website. Thank you for buying my patented EZ Bracelet!

If I want a 7 inch bracelet, does the bracelet sit on the 7 or the line above or below it.

Aim for the 7" or the 7 1/4" line. It's best to make a few samples for your own wrist so you get a feel for how much to add to the wrist measurement. Generally a beaded bracelet or a flat leather bracelet will follow this rule. but using toggle clasps affect it and so does using elastic. Instructions are on the EZ Braclet packaging and they're on my website too. EZBracelet.com

How accurate is this? I see such mixed reviews!

The one I got was not accurate and the adhesive is terrible on it. Others have said they use packing tape to hold theirs together. I tried stapling but that was not a great idea. Use a ruler or tape measure that is stuck down to your work area--THAT is accurate and what I now use. Just go 1/4 inch up and it will fit. 7.75 fits 7.5 inches etc.