If the blade is under 3 inches (and isn't lockable) you're allowed to carry it.
If the blade is longer than 3 inches you need a valid reason to carry it.
(2)Subject to subsection (3) below, this section applies to any article which has a blade or is sharply pointed except a folding pocketknife.
(3)This section applies to a folding pocketknife if the cutting edge of its blade exceeds 3 inches.
The three inches is clarification around folded pocketknives, it's not blanket authorisation to carry knives less than that length.