Jigsaw

A Jigsaw was a type of power tool used for cutting arbituary curves, such as stenciled designs or other custom designs, into wood, metal, or other hard materials. It is frequently used artistically, with one of its earlier uses being to create Jigsaw puzzle pieces. In fact, that was the reason why the puzzles were called "Jigsaw puzzles." Although they are good at curves, doing a straight cut is difficult even with a guide.

Usage
Big Boss, after forming and assuming command of the private military group, the Militaires Sans Frontieres, arranged to have a Jigsaw implanted into himself, which he disguised as a similar Snake-shaped scar to that of The Boss. He did this as a means to help himself escape in the event that he did end up captured by the enemy, and was unable to procure an alternate means of escape. He later mentioned after his escape from the Mine Base's detention center during the 1974 Peace Walker Incident that the next time he had to escape imprisonment, he'd like a jigsaw made of diamond to cut through the iron bars, with Miller jokingly asking whether there will be a next time.

Behind the scenes
The Jigsaw was an item that appeared in Peace Walker, which could be used by the player to escape from the prison cell, and is mandatory if the player failed to complete the QTE in the last portion of the prior mission. If the player utilized it during the the level, the conversation between Miller and Snake will be extended to have Miller and Snake reference the jigsaw, as well as explain that the scar that Big Boss had was in fact faked. To gain the Jigsaw, the player has to stand in front of a sink mirror and press the action button (the triangle button in the PSP and HD Collection PS3 version). Because of this special use, it cannot be found on Mother Base's R&D menu, either under the weapons category, the equipment category, or the special items category.