Originally Posted by
melslur
In other words, the left pedal has reverse threads, and the right pedal has normal threads.
Also, on my Shimano 520's, there is a "R" and "L" stamped on the spindle near the wrench flat and the pedal itself shows a tiny arrow indicating direction to tighten. Often, I have to wipe away the dirt/dust, squint, and get the right viewing angle to see it (but I refuse to wear bifocals).