I came up with a cusk/burbot trap design a few years back after losing too many fish and lines to chisel damage ! Here in NH we're allowed to have set lines for Cusk, only stipulation is that they have to be inspected once every 24 hours ! I use a scrape piece of 1/2 pvc pipe to prtect the line from the chisel and to help the line from freezing in. I use hole covers to keep the holes from freezing and it gives me a platform on top of the open hole to pile snow on for added insulation. I pour a splash of cooking oil in the plastic once the trap is in place and it allows me to check the line for a fish at anytime during the 24 hour period. The best part is no matter how cold it gets, to pull the trap to check it or move is very simple, I slide my chsel under the foam hole cover and lift, No chopping ! This set up has worked down to -34* below and makes checking the traps so much easier and it allows me to run more traps !