www.thedriller.com/articles/89948-solinst-versatile-well-construction-tool

Solinst Tag Line
April 20, 2015
The Tag Line is used to measure total well depth and the depths of backfill layers during well construction. It uses a stainless steel weight connected to cable laser-marked every ΒΌ foot or each millimeter, or PVDF flat tape laser-marked every 1/100 foot or each millimeter. The weight can be clipped off, allowing the Tag Line to be used to lower bailers or other devices. www.solinst.com