Modern knife steel is very high quality material, but all metal will corrode through time. Occasionally oil the joints and springs of a folding knife with a drop of oil. Carbon Damascus needs to be kept in a light film of oil, as it corrodes very easily. This will assure easier opening and closing and will prevent rust and lessen wear. Wipe the blades now and then with an oil-moistened cloth to prevent rust, especially if you live in a damp climate or near the ocean. If your blade should get wet, dry it thoroughly as soon as possible. If your knife comes into contact with salt water or any substance you are not certain about, you should rinse it immediately with tap water and a mild detergent, dry it, and apply a light coat of oil.
Check the locking notch of lockbacks regularly to ensure that it is working properly. Keep all sand and grit out of the knife. Keep the mechanisms clean. Remember to never rely on a folding knife to be permanently locked in the open position.

Do not use the blade as a can opener, chisel, pry bar, screwdriver or for any heavy work for which your knife was not designed. Don't use the back of a knife as a hammer, as that may break the springs, handles or pins.
Handles made of wood can be occasionally rubbed with furniture polish or oil. Warthog tusk, Hippo tooth ivory and bone should be rubbed with baby oil. Brass and stainless steel can be polished with household polish.
Remember to keep your knife sharpened -- a dull blade can be more dangerous than a properly maintained one.
Knives should not be kept in their sheath for prolonged periods, as the tanning acid in the leather may stain or pit the blade.