A rigid box is a board before it is a surface. Greyboard or chipboard is cut to a net, then grooved. A V-groove takes a wedge out of the corner so the board can fold to a right angle and still keep enough material to stay plump. The corner is pressed. Only then is the wrap glued and spotted onto that carcass.
The wrap is a second system. It covers. It does not square the corner, and it does not make the base. If you draw a soft box with round, unpressed corners floating in empty space, you have skipped the carcass. The picture cannot be produced as a rigid box, because the object in the picture was never a board.
Say the order out loud when you review a pack: cut, groove, press, wrap, stand.
How to check it
- The corner in the drawing is a pressed right angle, not a blob.
- You can point to the groove that let the board fold without breaking the face.
- The wrap is described as glued onto something that already stands.
Usage
.corner {
/* A pressed edge reads as two planes, not a radius. */
border-radius: 0;
box-shadow: 8px 0 0 -7px rgb(20 19 14 / 0.18);
}