No, they’re not special headgear that the barber wears to entertain young customers. Clipping masks are simple, yet incredibly handy, Illustrator features. Simply put, they hide things. Like Effects and Transparency settings, Clipping Masks are live functions that make no permanent change to path data. They make things look different, but you can take them away with a single command, and your paths remain exactly as they were before.
Clipping masks use objects to hide other objects, as shown in Figure 10-16. The top object (the masking object) becomes completely transparent. The underlying objects become invisible except for where the mask object is. The number of objects beneath the mask doesn’t matter. Only the topmost object functions as the masking object. The top object’s fill and stroke also don’t matter, because the top object becomes invisible.
To create a clipping mask, here’s the drill:
Create an object to be used as a mask.
Masks can be any shape or color. You can even use text as a mask.
Position the object in front of whatever you want to mask out.
Select the object and all the objects behind it that you want to mask out.
Shift-click with the Selection tool to select multiple objects.
Choose Object→Clipping Mask→Make.
The masking object and anything outside the mask disappear, leaving just what’s inside and behind the masking object.
The things that seem to disappear after you apply the mask aren’t really gone. They’re just hidden. You can bring them back by choosing Object→Clipping Mask→Release. Sometimes that’s more impressive than pulling a rabbit out of your hat.