How to copy 1 part of a mesh to other places on the same mesh (without mirroring) Firstly, I'm new to blender so apologies if this is a really  newbie question.
I'm trying to copy part of a mesh, and apply that to other areas of the same mesh. (On the image below, I'm trying to repeat the recessed area on the left, to the selected faces on the right. I know mirroring is a possible option, but I need to also repeat it elsewhere where mirroring isn't possible, so trying to learn how to do a more &quot;copy/paste&quot; approach)
I've tried following some previous posts which advise using shift + D to duplicate the faces of the object, then move the duplicate away from the mesh, then right click and do separate &gt; selection.
However, when I do that I get a red border around the new object and when I select the new faces (the destination) I can't seem to get it to apply the shape (I also can't &quot;grab&quot; the new item to move it).
Any ideas where I'm going wrong?
Also... how do I stop the mesh from vanishing &quot;inside&quot; the object as visible in multiple places in the image below? It's making it really hard to work when I cant see/select all of the vertices, etc

Thanks!
When you separate the selection, you're actually creating a new object. It seems what you want to do is to split. You don't need to split the part since you have already duplicated it. If you want to &quot;cut&quot; it without copying, and keep it in the same object, what you need to do is right-click and choose Split &gt; Selection - Y is the standard keymap.
Once you duplicate the part, place it somewhere, then the easiest thing to move it where it is intended is to select vertex mode, then deselect and reselect a vertex on the duplicated part (while making sure that the part is still wholly selected), activate vertex snap, and move it to snap with the correct vertex at its intended location.