Hi, if I understand you right you could, with 3 video layers have the same clip on the top two layers, add an edge wipe to the top layer, double click the wipe and make the start and end the same percentage, say 50%, feather the edge and make the duration of the wipe the duration of the clip. You now have a static wipe. Reduce the opacity of the clip underneath using the clip overlay (option w). Place another clip underneath which will show through. Just one of many ways to do this.
Thanks for the advice I've never used a wipe in that way before it's a clever idea. A simple way for linear masks any way. I wish they would put a pen tool for drawing your own masks in FCP itself. my system can't handle Motion all that well.
I know, maddening isn't? How hard can it be? Every time I work on Avid I realise how much I use animatte. There is a free plugin called 50 point bezier matte (search for it). It is fiddly but if you make a random shape with loads of points and save it as a favourite you can then use it when you need it. It is still a bit of a pain because you have to keep selecting the points in the viewer before you adjust them in the canvas.