For the purposes of this section, "switchblade knife" means a
knife having the appearance of a pocketknife and includes a
spring-blade knife, snap-blade knife, gravity knife or any other
similar type knife, the blade or blades of which are two or more
inches in length and which can be released automatically by a flick
of a button, pressure on the handle, flip of the wrist or other
mechanical device, or is released by the weight of the blade or by
any type of mechanism whatsoever. "Switchblade knife" does not
include a knife that opens with one hand utilizing thumb pressure
applied solely to the blade of the knife or a thumb stud attached to
the blade, provided that the knife has a detent or other mechanism
that provides resistance that must be overcome in opening the blade,
or that biases the blade back toward its closed position.