Boolean trouble: union and intersect work, difference doesn't Newb here.  I'm going through Blender Guru's intermediate tutorial and have roughed out an anvil.  I've created a cylinder to subtract form the side of the anvil using a Boolean difference modifier.  The modifier is having no effect, though switching it to union or intersect causes it to do what it's supposed to.  I've confirmed that all normals are pointing out.  I'd attach the file but I don't see any way to do that (screenshot of what I'm looking at below).  Hopefully my description is enough for someone to point me in the right direction.  Thanks.
You have overlapping vertices that prevent the boolean, select your anvil, go in Edit mode, press Alt &gt; M &gt; Merge By Distance, and it will work.