Just want to add a little note about which side of the ruler goes in and which side out. Believe it or not my girlfriend made hers and put the numbers on the inside and it didn't work. It turned out that she had a tape measure with the numbers on the outside of the concave - I saw it with my own eyes - had to - LOL - thought she just didn't understand. I wish I had taken a picture of her tape measure next to mine - one with numbers on one side and one with numbers on the opposide side of the convave. So maybe we better say to have the outside of the concave facing the outside of the purse and the hollow side of the concave facing the inside just in case someone else gets hold of a tape measure like she has.