Learned from Rick Hobbs, Clearwater Lake Lodge,Manitoba, Canada. Put puff of air in tail of crawler and it will float above bottom where it can be seen by trout. Insert number 10 short-shanked hook into head of crawler and run point down as deep as possible then bring point and barb out of crawler. Push crawler's nose over eye of hook and onto leader. Good on fish 16 inches and bigger.
Smaller fish tend to just bite off crawler.
Two Loons Lake, Manitoba, June. This method took 10 Master Angler rainbow trout for Bob Brown and me when no other presentation would work. Spring and early summer pattern before fish leave weeds and move to mid lake reefs. Find sand banks where pike weed grows . Fish in front of pike weeds over coontail beds.