|This article is about an older version of DF.
A block is a type of building material. Stone and wood can be shaped into blocks at a mason's workshop or carpenter's workshop. Glass can be formed as blocks at a glass furnace, ceramic blocks (labeled as "bricks") can be made at a kiln, and metal blocks can be made at a forge from a single metal bar (or, in the case of adamantine, from four wafers). Blocks do not have quality levels.
A single block is required in order to build a well, screw pump, or ashery. Blocks can also be used in place of raw stone or wood in roads, bridges, workshops and constructions (but not in items like crafts or furniture). Stone blocks are sometimes used as materials during strange moods.
Blocks vs Rocks
Building a bridge out of blocks instead of rocks cuts the building time by two thirds, independent of clearing and hauling time. This difference in building time presumably extends to other buildings and constructions where you can choose between blocks and rocks.
Blocks weigh less than the material they're made from, being anywhere from 1/28 to 1/31 of the original weight.
Blocks are more valuable than rocks. Blocks have a base value of 5, compared to the raw material value of 3 for stone, wood or glass. Metal bars already have a base value of 5.
Some players prefer to build workshops from blocks instead of rocks to avoid a surprising feature of forbidding. Players often want to control which types of stones their workers use, especially at mason's workshops and mechanic's workshops, to control the color of the resulting furniture. One way to achieve that control is by mass forbidding whole types of rocks from the stocks menu. But if you forbid the stone (or block) that a workshop is made of, then that workshop will no longer function. So a player forbidding stones to produce a particular color of chair or lever is often surprised when other workshops suddenly stop working. Building workshops exclusively from blocks allows the player to mass forbid rocks from the stocks screen without encountering this problem. Building out of blocks also increases the value of the workshop, which increases the wealth of your fortress.