I couldn't find a hook strong enough for the heavy icicle lights I bought.  They were either to thin and wouldn't hold the weight or they were to flimsy and would not stay under the shingles.  Wind would inevitably blow the lights down.

I designed this clip to be able to withstand the heavy light strings and not come out from under the shingles.  I have used them for the last three years with no failures.  I also included a screw hole in case you want to screw them into the eve and leave them up all year, as I have done.  (no more ladders)

Either print them in a color to match the house or paint them.