Mikov knives is the one the oldest and the larges knife mfg. in the Czech Republic. They have been in existence since 1784 and are well known for their line of automatic knives. The Mikov Predator autos use a flat lever to fire them. The lever is flicked up with your thumb and then depressed forward to fire the knife. They use dual leaf springs that are removable form the rear of the handle. They are well made and quite addicting to fire. These are not that common here in the USA.  Click the link below for a short video firing a Mikov.