Ryan Maloney shows three ways to draw inside a shape in Procreate without going over the edges: using Select to constrain strokes, turning on Alpha Lock to draw only on existing pixels, or creating a Clipping Mask layer to keep new marks contained.
Chapters
If you have a shape drawn in Procreate and you want to draw over that shape, but you don't want to overlap the edges, here are 3 ways to do it. The first way is to select the layer. Open up your layers palette, tap the thumbnail of the layer you're working on, hit select. Now you just draw on top of the shape and you won't go over the edges. The second way is alpha lock. I'm going to go into my layers, hit alpha lock. I can draw seams here and not go over the edges. The third way to do it is to create a clipping mask. Go to the shape you want to draw on, hit new layer, tap that new layer thumbnail, go down to clipping mask, and you'll see this little arrow pointing to the bottom layers there. Now when I draw, I'm not drawing anywhere outside of that layer. I'm drawing inside of it.