Jack Knife is a grey Earth Pony with a black mane. He has magenta rings around his eyes. His eyes are a pale blue. Jack Knife has scars on his lip and his right ear is torn. Jack Knife wears a bear belt.
Jack Knife is anti-social just like his brother and prefers to be left alone. He is mentally unstable and needs to be constandly doing something, usually with his hands like sharpening his weapons.
Jack Knife is closely bonded to his younger brother Cutthroat. The two of them are known as the Black Smith brothers by the rest of the clan. Together will force weapons and search for materials. Jack Knife likes to pick up bones to make bone armor with. He has a fondness for dragons and their shiny scales.
Jack Knife and his brother Cutthroat were ophrane in their teen years. Jack Knife took care of his younger brother and taught him how to make weapons out of metal and bones. Recently Jack Knife accept Hijack as his mate.
- Jack Knife is named after a recurring character seen in Super Jail. Jack Knife is a type of knife with a folding blade. It's also a kind of sea shell and when a large truck becomes pushed and bends sideways by it's trailer.
- He likes the taste of metal and will lick his knives often or any other kind of metal around him. He will lick rocks to see it they contain any metal properties.