Why do I have to use negative solidify values when the tutorial does not? So, I was following this blender tutorial and the first time I did it, it went swimmingly.  Now I have a problem: whenever I copy the top of the doughnut and solidify it for the icing... the thickness goes INISDE the doughnut.  This means that whenever I snap the icing to the face of the doughnut when trying to make the icing look runny, it always goes inside even when snap works.
Whenever I use the positive thickness, I get this problem:

But whenever I set the value to be negative: it nearly fixes this problem.

I have no idea why.  Could someone please point me in the right direction?  This almost works, but it still leaves the issue of the &quot;Crease&quot; setting not quite working properly.
It must be because his faces normals point inwards while yours point outwards, you can check the faces orientation if you enable the Face Orientation option in the Viewport Overlay panel, the blue face means normal positive orientation, red face meaning normal negative orientation. To recalculate inside, select all in Edit mode and press ShiftCtrlN, to recalculate outside, ShiftN.