If you look carefully at Figure 21-12, you see that the cylinder has a top but the triangular prism and the box don’t. AutoCAD puts top and bottom surfaces on some objects with thickness, but not on others.
Če si pozorno ogledate sliko 21-12, lahko opazite, da ima valj pokrov, trikotna prizma in kvader pa ne. AutoCAD na nekatere predmete z višino postavi pokrov in dno (zgornjo in spodnjo površino), na druge pa ne.