|Alias(es)||Cardboard Box Man (superhero pseudonym)|
|Eye Color||Forest Green|
|Relative(s)||Butter Knife (younger sister)|
|Voice Actor||Unknown (Online episodes)|
Yuri Lowenthal (Jimmy Benedict, TV series)
- "Man, don't tell me what to do, man!"
- ―Jack Knife, The Lost Skate Spot
- "Whatever, man."
- ―Jack Knife, Grindermania
Jack Knife is one of the main characters of Wild Grinders.
From the old Wild Grinders site:
Jack Knife is a legend at the local skate park. Wild Grinders prefer the streets, but the park is always a guaranteed no bust spot for Jack Knife. Jack Knife is an all around shredder who will tackle anything. He isn't the most technical skater out there but he will gladly skate anything. The less wax on a ledge the better. Jack Knife is the gnarliest skater in the Wild Grinders.
A lumberjack-themed character have his lack of knowledge, before getting himself injured or resembling into the Grinders' disappointment. After Jack Knife finishes his sentence, he ends with "man", as his speech was suggested to be talking to his friends, except for girls as he ends with "m'am". Jack Knife acts gullible infront of others, and commonly does not know how to use the controls on electronics. Jack Knife is able to break fragile props easily, such as china, glass, and marble; however, one of the Grinders seized him as he was strapped or locked. This process avoids breaking the stores' properties.
In Grindermania, His musical instrument is the guitar, but Jack Knife plays it wrong as he wanted his guitar to sound like a saxophone.
The official site claims that Jack Knife's stance is regular, and he prefers to skate on "anything and everything. As long he can skate it FAST!". His favorite music is "The more METAL the BETTER!", as of older information.
- Steak Knife-Jack Knife's father.
- Bread Knife-Jack Knife's mom
- Grandmother-Dialogged by Jack Knife in Scream a Little Scream. Her house reminds Jack Knife's neighborhood.
- Butter Knife- She is introduced as Jack Knife's younger sister.
- Prince Xavier-Jack Knife has his royal look-alike to swap places to help him during the Royal Tournament Cup.
- Crash Basher-Jack Knife's idol whose true identity is unknown. Despite of being his idol, Crash held a spite and molested him usually.
Rarely, Jack Knife almost look like a lumberjack, but was approved to be retro. He wears a red plaid shirt and brown shorts. He had a blue hat that can match up with his tennis shoes. Also, Jack Knife had a gap on his left side of his teeth that makes his tooth hang while closing his mouth. While going outside at the shore, he had his shirt taken off and wrapped it around his waist. Jack Knife's skateboard is blue with checkered patterns and yellow wheels.
In Lil Red Riding Rob, Jack Knife was formed as a Gingerbread Man.
When Lil Rob travels to another dimension in A World Gone Rad-Awesome, Jack Knife has his opposite self as savvy, genius, and nimble. He accessorizes himself with a yellow tie attached to his red plaid shirt. When combining by Spitball in an unbalanced time, it takes Jack Knife's head and Spitball's full body, with his sunglasses and bandanna.
In the second half of the Halloween special, Scream a Little Scream, it seems that Jack Knife is wearing a hockey mask; however, the plaids of Jack Knife's shirt was removed.
Unlike Jack Knife's appearance in the television series, Jack Knife's hat was printed as "DEFCON" and can be shown on the wallpaper only. Instead of blue-checkered patterns on Jack Knife's skateboard, it have a yellow checker-pattern with a sky-blue section around the edges. The skateboard's wheels are blue instead of yellow.
Jack Knife's name is based on a type of pocket knife, a miniature weapon, or an exercise.
In the Brazillian adaption by Gloob, from Globostat, Jack Knife is named as Canivete. This Brazilian translation includes his original name, pocket knife, switch blade, clasp-knife, pen knife, and basically a knife.
- Both Emo Crys and Jack Knife prefer to skate on mini-ramps, vert, and bowls.
- The new version of the Wild Grinders official website stated that Jack Knife can prefer to "skate anything that he wants as he can skate it fast", and his stance is printed as regular; however, Jack Knife's stance is goofy and he prefers to skate on mini-ramps, vert, and bowls, as said in the revised version Wild Grinders' official website, preceded by Lil Rob, Spitball, and Emo Crys.
- Although Jack Knife's voice is stammered in the online episodes, he speaks in a southern accent in the TV series.
- On the merchandise, Jack Knife's skateboard was mistaken as a yellow-checkered pattern and blue wheels, instead of blue-checkered patterns and yellow wheels. like on the TV series.
- Jack Knife was reminded that he have his skateboard departed or stupid; for example, one of Jack Knife's yellow wheels are replaced by an uneaten bagel, as seen in Golden Grinders.
- As dressing up as Prince Xavier in The Prince & the Skateboarder and Jay Jay in Swaggerless, Jack Knife is the first of the characters who dressed up as of the other characters' original appearance.
- Ironically pointed in It's Not My Asphalt!, Jack Knife listed lawn gnomes as one of his dislikes.
- Jack Knife's quote "I love (Jack Knife's favorite moments), man!" is a running gag for several of episodes' endings as of Season 2.
- As explained by Grindbox 1080: Game Over, Jack Knife speaks Japanese in the wrong direction. Neverless, he have spoken this language correctly in The Luck of the Grindish as his wish, but mistakens it as a misunderstanding.