not there Bewertet mit 1 von 5 Sternen

installed it and its on my add-ons list and enabled however, its not showing up in the ad on bar. booooo

Diese Bewertung wurde für eine vorherige Version des Add-ons ( abgegeben. 

Thanks for the feedback! Though I wish it didn't merit a 1 star rating (ouch!) you can right-click on any toolbar in Firefox and choose "Customize". In there you'll find the MeasureIt ruler icon that you can drag to any toolbar you choose.

I hope to create an update that will auto place it in the add-ons toolbar soon.