To paraphrase cybrok, in the Criminal Code:
ILLEGAL: switchblades, push daggers, knuckle-duster knives, flick/gravity knives, concealed knives, etc.
LEGAL: non-prohibited folders, fixed blades, waves, thumb studs/disks/holes, serrations.
I'm not sure about balis. AO's seem to be technically legal (but too borderline for my comfort).
If anything you carry is intended for SD, it's automatically classified as a weapon, hence illegal. Concealing said weapon will only add to your woes.
Remember, local city ordinances may vary.
There's no actual legal limit on length in the Criminal Code: it's open to interpretation of intent, so be reasonable. Remember, in Canada, a legal knife is a tool only. Personally, as much as it pains me, I restrict myself to 4" around Hogtown. If I'm on-site in one of the downtown towers, I'll go so far as to carry just a multitool and leave the 4" deep in my pocket or backpack (I once had some paranoid secretary call security on me because she saw me walking the secure floor with a half-dozen phones in my arms). I don't get out much, so I'll let someone else tell you about the other insignificant parts of Ontario .