abigs,
Essentially, you're right.
According to the Attourney General's office, It's legal to carry
concealed, an "ordinarry pocket knife" with no blade more than
4 inches long. Such knives are not considered "knives" under Mo.
law. There in apparently no provision for concealed sheath knives,
and I suspect that we must presume "ordinarry pocket knives" to
be slip joints.
As for CCW. Mo's CCW law has no specific inclusion for knives
or other weapons.....just firearms....BUT, if one has a CCW permit,
Concealed knives, other than ordinarry pocket knives, are not
criminalized.
Open (non concealed) carry of sheath knives does not appear to be
restricted by state law.
Most city and county ordinances (but NOT all) are no more restrictive
than state law.