Blocks are reusable content that can be used again and again in a drawing (and in other drawings). You can make these blocks and then save them for use in other drawings. An example of a block is shown here:

In this drawing, the chair, doors, desk, computer, and telephone are blocks that have been made once and used repeatedly wherever needed. Though there are many advantages to using a block over simply copy-pasting the original symbol, the biggest advantage is the ability to modify all references of the block by modifying only one block. In the preceding drawing, if you happen to modify the chair, all the instances where the same chair block is used will modify automatically to reflect the changes made by you in the first block. In this section, we will start by making a simple door block and then move on to use and modify it.