"Blocks" are a feature of DesignCAD that allow you to define a collection of objects as a block and then make multiple copies of the block throughout the drawing. After this you can change ALL copies of the block by just editing the original block. So if you have many copies of a particular object, say a door latch or light fixture, and you want to replace them all with a different door latch or light fixture, all you have to do is edit the original block.

Blocks also have the property that only one complete block exists in a drawing and all other instances are just small place holders. This makes the drawing smaller so it takes less disk space and loads and saves faster.