How do I limit effect to subset of clip's frames?

If I bring a clip into Fusion and let's say I want to mask part of it but I only want the mask to be active for say 10 frames, how do I enforce a limit like that? Previously I end up cutting the clip up so that just the section I want affected goes into fusion but I know there must be a better way!

Thanks!

Depending how you set up your comp and the kind of mask you can move it out of the way or animate the level slider.

Thanks Sander - Moving the mask out of the way was it

Also if memory serves me correctly (which is usually doesn't) in the merge type field there is a 'ignore' option which you can animate. I personally wouldn't move it off screen because it still exists in the DoD and although you can't see it Fusion may still be processing it.

So best practice is to move the Blend slider in Settings to 0? I usually just move the mask off screen but who would want to be processing anything unnecessarily.

Best practice purely depends on your use case. I've never spent too much time optimizing my comps, because I'm not a hardcore compositor. If there's nothing to process for Fusion it won't process, but I don't know how much difference it makes if you have a small or a big DOD for the average composition.
I know that there are also people who go into the keyframe editor and drag the in/out bars of tools to limit their effects, but personally I've always found that too much bother.

Come on guys, I can understand that specific "best practice" may not be overused but hey, the OP writes about a mask which should vanish/be ineffective at a special time...
Seriously ? Of course he should use the blend or level cursor and add a couple of keyframes : 100 here and 0 there, et voilà

My first job as a roto artist drilled into me that moving the mask off-screen was a no-no because of motion blur.

Animating the Level is what I usually do, but you have to remember to change the Paint Mode to Maximum so a mask that you set to 0 doesn't carve a hole in the combined matte.

Can't say I'm that bothered either but if it's as easy to save a few clock cycles as not, then we may as well save some. If you are rotoing people you could have a few dozen on the go quite easily. Maybe i'll test one way against the other and waste as much time doing the test as could be save one way or the other.