Pickslanting Concepts
Not only do picking motions often move along a diagonal path, but when this happens, the pick itself frequently assumes a diagonal orientation.
A Tale Of Two Slants
Here’s Marty Friedman’s famously recognizable picking hand setup:

The slant of the pick toward the left in this closeup shot is pickslanting. Specifically, this is downward pickslanting, after the way both the pick and the arm itself slouch toward the floor to achieve the orientation. We sometimes abbreviate this as DWPS for short.
The inverse orientation is upward pickslanting or UWPS, in which the pick appears to slant toward the ceiling. Here’s sweep master Frank Gambale:

At first glance these two opposing orientations might seem pretty unorthodox. Why would you do something like this? After all, wouldn’t this have some effect on the way the pick hits the string?
Slant Versus Motion
Indeed it does. In fact, that is the whole point. Remember, these players aren’t actually picking parallel with the strings — they’re picking on a diagonal. Here’s a short loop of Frank’s DSX motion:

Frank’s primary alternate picking motion is DSX, featuring a characteristic single-escape trajectory. In this example, the downstroke begins trapped between the A and D strings, and finishes in the air above the G string, in the escape zone. The upstroke is the reverse, traveling from the escape zone above the G string to the trapped zone between the D and A strings to start the motion over again.
That’s the motion. The pick’s orientation is UWPS, clearly slanting upward, toward the right side of the screen. To figure out why he’s doing this, let’s rotate the camera until the pick appears vertical again with respect to the screen:

With a 20-degree rotation of the camera, we’ve dialed out Frank’s upward pickslant, restoring the pick to vertical with respect to the screen. But we’ve also done something else we didn’t expect: we’ve made his DSX motion parallel to the screen. This shows us that in some sense, Frank’s pick wasn’t really slanted at all. Relative to the picking motion, the pick was actually perpendicular:

In rotated view, the pick is vertical and the strings are diagonal. As far as the pick is concerned, it’s really just moving side to side, and upstrokes and downstrokes are perfectly symmetrical in their approach to the string.
Pickslanting In Practice
The term “pickslant” has the word slant in the name. But this can be a little misleading. In actual practice, you don’t always have to take additional steps to “slant the pick” to achieve pickslanting. For most picking motions, the simple act of assuming the body positioning and pick grip necessary to perform the motion is enough to create the correct pickslant.
Once you achieve this general body positioning, you can still make minor adjustments to the pick and its attack, including its pickslant, with changes to your grip and arm position. But these changes will be small enough that you can probably focus on learning to create the motions themselves, without worrying too much about the pickslant.
Instead, a more general awareness of what different pickslants look like can be helpful in understanding why certain techniques look the way they do, so it’s not confusing to you when try to learn them. In the next few sections, we will take a look at some common picking motions and the pickslants they use.