Pickup covers?

I have a faded sg without covers.
I have heard adding covers would tone down the "brightness."

Anyone know for certain what effect if any they'd have?
http://www.marshallparts.com/pictures/600b/Pickup-Cover-for-Humbucker.jpg

I could also accomplish this by swapping caps in the tone circuit but do not wish to fuck with OEM stuff.

Yep, it'll dull the output just a smidge, and it'll also reduce the highs you get out of it. The effect is better controlled using caps.

The length of cable you use is also important. To reduce perceived highs, try using a shorter cable.

i guess the covers make the magnets move and that affects what they pick up... someone explained it to me once but i dont remember how it works

i guess the covers make the magnets move and that affects what they pick up... someone explained it to me once but i dont remember how it works

There are holes to allow the magnets to protrude.
Move?
How so?