Mask & Masked Effect

Your first layer masked then you insert a keyframe on frame 40. Then you add a new layer, and name it mask. You insert a keyframe on frame 40. Then on your masked layer you draw or type whatever you want. You then create a shape that is bigger than your drawing or text. On mask layer go to modify timeline and layer properties click on mask and then lock it. You then insert a motion tween and on the mask layer move your drawing or text on frame 40. Then you click on the masked layer and go to modify, timeline and layer properties then click on the masked and lock it.