One side of the file is double cut. The other is single cut. You should know immediately which side is which by looking at it.
Double cut is used for quickly shaving off material.
Single cut is used for "smoothing". I recommend you use only the single cut side for standard edge tuning.
The double cut side will need to be cleaned often (with a file brush or other cleaner), whereas the single cut side will "clean" itself during use (mostly).
Always go "against the grain" when filing. Going the other way will dull the file. The Dakine file pieces have an arrow showing you which way to pull the file.
Also pay attention to any numbers on the plastic tool itself. 90 is a straight right angle, whereas 88 will bevel the edge 2 degrees inward.
THERE ARE SPECIFIC REASONS AS TO WHY I AM MORE LOCAL THAN YOU
GOD IS DONUT