Flint and Steel

Flint and Steel is a tool used to place Fire in Indev, Infdev, Alpha, and Beta. It must be crafted from 1 flint and 1 iron ingot in this pattern:

Use
When used with right-click on top of a solid, fully opaque block or on the sides of a flammable block, flint and steel places fire in the air block directly ajacent to the surface on which it is used. In Survival, it can also be used to break TNT with a left-click. When broken in this way, the TNT drops primed TNT which will explode. This does not work in Creative as this special effect of flint and steel on TNT is not resolved. A flint and steel has limited uses. When right-clicked to place fire, a point of durability is drained whether or not the surface it is used on is correct for the placement of fire. However, as it is not a block-breaking tool, it can be used without damage to break blocks using left-click.

The firestarting ability of Flint and Steel makes it a versatile tool and weapon. Despite the reduction of its spread, fire can still be useful for some clearing jobs. It will quickly remove fences or wooden stairs (in a roof for example), clear wooden or cloth floors for renovation or thin out overly dense areas of forest. In most cases the fire will not cleanly remove all unwanted blocks, so final clearing with another tool is necessary. It has the advantage of working on its own while the player can do something else productive.

As a weapon, fire can be started beneath a mob or in a mob's path as a damage-over-time attack. For some pursuing mobs, this provides a "ranged" attack that does not expend arrows nor has the inherent danger of attacking in melee. The underlying block need not be flammable as the fire will still last for some time. Against Spiders or Endermen, the flint-and-steel can be used to cause damage without pulling aggro. Whilst afield, it can be used to convert any nearby animal into suitable rations without the need for fuel or furnace.

Flint and steel has good synergy with netherrack and as such is the predominant lighting tool while in the nether. This use can be extended back to the overworld by carrying netherrack, which provides brighter light and damage potential compared to torches. Additionally, fire can also be used to quickly dispose of unwanted items by dropping them and lighting them on fire or by using netherrack to make an everlasting incinerator with fewer containment issues than lava. Flint and steel, along with fire itself, explosions and redstone are currently the only ways to activate TNT as of 1.7.

Flint and Steel requires a single iron ingot to manufacture, implying some degree of resources already established and as such may not be available early in the game depending on the player's direction of play. Over the long term, flint and steel tends to be a very minor expenditure of iron or flint compared to those resources' other application.

Trivia

 * In early versions of Indev, the player started with a flint and steel in their inventory. Flint and steel was also found as loot from killing mobs.
 * In the start of Survival Multiplayer, furnaces did not work. There was a mod that turned flint and steel into a "lighter" that lit the furnace and made it work.
 * Prior to 1.6, fire could spread indefinitely, making flint and steel an effective weapon of mass destruction in areas with large, interconnected sections of flammable blocks. Many servers banned and continue to ban the use of flint and steel as it can be used for griefing. Following 1.6, fire no longer spread infinitely.
 * Before furnaces, flint and steel could be used to smelt ores.

Now try to set the highest block of the wall on fire on the side which is closest to the block you want to burn. This will result in: (Note that the furnace is on fire, not the wall.).
 * There is a way to set workbenches, chests, furnaces, and dispensers on fire. Any other solid and opaque can be set on fire like this. To do this, copy the shown building (side view) (You can do this with any blocks, but the wall must be made of unflammable blocks, and all blocks must be solid and opaque blocks)