Sharpening with triangular files?

[Pierreg]

Several years ago I read an article about a Husqvarna expert(can't recall the name). He wrote an article about the danger of running dull chain.He had an unusual way he sharpened. He set the saw with the bar pointing up and went around the bar in one direction then flipped the saw bar&did the other side. I think he used triangle not round files.He touched up his chain and it was very sharp. Anyone know of this style of sharpening?This guy was a wiry Swede and he swore by the triangle files. Any info on this? Thanks and keep warm.

 

[mtngun]

Sounds like square chisel chain, what most pro loggers use for softwood.