Abstract: Knives configured to use interchangeable blades, blades for those knives, and methods of making an using the knives and blades are disclosed. One knife includes a latch assembly that retains a blade in a slot of the latch assembly using a dual-stage locking mechanism wherein two different latches must be operated to exchange the blade in the slot. One latch is a button that translates a pin through the slot, and the other latch is a rocker lever that rotates into and out of contact with a notch, recess, or groove in the blade. The first latch controls movement of the second latch in order to help avoid inadvertent removal or dislodgement of the blade. Some blades include multiple notches or recesses so that they provide multiple points of contact that resist translation and rotation of the blade out of the slot, even when subjected to unusually-directed forces.