I was in the bow shop last night and saw a tool that snapped onto the string that had a sliding pointer on it. You snapped it onto string at the nock point then slid the pointer up to where the peep sight was and you could take the device off and always had the measurement for that bow. I was wonder if anyone knew where to come up with something like this.

I have ran a search on web and didn't come up with any advanced bow tools just the normal noc pliers and ect.

I should have asked the guy where he got it but we got to talking and I forgot to.

Thanks
Jeremy