CRACKJACKS
CrackJacks were developed in the 60's by Peter Haan and Les Wilson for protection in off width cracks, specifically, the right hand side of the Hourglass in Yosemite. They received little attention at the time. They were available at the Ski Hut, but it is not clear how many if any were sold. For this purpose they are probably the best device available to this day.
The original CrackJacks were made from an iron turnbuckle. The ends were cut off and replaced with a short section of angle. Two sizes were made, making possible protection of cracks from 8 inches to sixteen inches. The sides of the crack needed to be reasonably parallel for this model. They were quite inexpensive to make.
The second model was made of high alloy aluminum. They were adaptable to irregular cracks as both heads were swiveled. The barrels were also interchangeable. With a pair of heads and a variety of barrels, cracks of any size could be protected (up to the length of the longest barrel plus about 4 inches).
The pictures are icons. Click for high resolution.