A slipjoint knife is one of the most ubiquitous types of pocketknives.

A slipjoint knife consists of a handle with one or more folding blades. These blades are held in position by a strong "backspring" which biases them towards the open or closed position. Contrast this with the penny knife

Penny knife

The penny knife dates from the 18th century and was an extremely basic utility knife, originally with a fixed blade. It received the name penny knife for what it reportedly cost in England and America during the late 18th century...

, which has no locking mechanism other than friction, or the lockback/"buck

Buck Knives

Buck Knives is an American knife manufacturer founded in San Diego, California and now located in Post Falls, Idaho. The company has a long history through five generations of the Buck family from 1902 to the present day...

" knife which mechanically locks the blade with a lever.

Legal status

In several countries, such as the United Kingdom, slipjoints are used over locking folders due to laws regarding carrying knives for general use. In Germany, because the use of locking one handed opening (OHO) knives is restricted, slipjoint knives are a viable alternative.

American slipjoint knife variants

The United States produced a massive array of slipjoint knife models from the mid-19th Century to the present day. The following is a list of representative models and their defining features:

• Peanut -- a very small (3" or less) pocketknife, with a slightly irregular ovaloid shape resembling an elongated peanut. Generally with two blades of different sizes/profiles opening from the same end.

• Barlow -- a medium-sized pocketknife of tapered oval construction, with two blades of different sizes/profiles opening from the same end.

• Sunfish or Elephant's Toenail -- a small pocket knife with a very wide body usually having two blades one of which has the same wide body as the handle. The blades usually open from either end.

• Congress -- a small pocket knife with shallow concave back and shallow convex top. Usually carries 4 blades opening at opposite ends.

• Sowbelly or Stockman knife -- a medium sized pocket knife 3" to 4" with bend in the body. Usually carries three blades with two clip points and a spey point blade being a common configuration. Blades usually open from both ends.

• Canoe -- a medium sized knife 3" to 4", rather wide with a slight curve. Generally with one large and one small blade at opposite ends.

• Trapper -- a medium sized pocket knife with a rounded end and which tapers slightly towards the knife end. Usually carries two blades with a clip point and a spey point blade being a common configuration. Both blades open from same end.