Interestingly, there were several steps involved in the slate installation that roofers in the U.S. almost never encounter. For one, the roofer Toronto was obligated to "hole" each slate, as no nail holes are punched in the slate at the quarry as is typically done in the U.S. This is a carryover of the days when graduated slate roofs were the norm and nail holes had to be punched in the slate on the job after the proper overlap had been determined for each diminishing course. The position of the holes in the slate was particularly critical when using lath, which left little room for error. Sawn lath strips developed from the practice of using hand split lath, as mentioned earlier, and continue, to this day as much from tradition as from a lack of lumber resources in England and Wales.
But another surprising practice was the sorting of the slate prior to installation. This was a roof of uniform sized slates- not a graduated slate roof. Yet, the roofer, according to custom, sorted the slates according to thickness before carrying them up onto the roof, the thicknesses being termed "very heavies," "heavies," "mediums." and "lights."
