All AutoCAD versions. This article prepared by ADT 3.3

Blocks are entities that make life much more easier for AutoCAD users. Although most of us use AutoCAD in an active way, we don’t use blocks that much and make our drawing time pretty longer. In this article, I will explain what the use of blocks, what kind of easiness they provide us, and how they are used.

Block is an entity, which is a combination of the entities that we select among the entities in the drawing as referenced to a specific point. Number of blocks we insert into the drawing has no influence on file size. For example, if we are using 40 number of the same window in a drawing, then drawing each one or copying and pasting each one means that they occupy the same file space 40 times. Instead, if we make a block from the window we are drawing, and use it 40 times where we need to draw one, they will occupy file space equal to the space occupied by only one window. Number of windows we place inside the drawing will have no influence on the file size. By this way, we can make the large drawings that we are working on, lighter and easier to work on. Another useful feature of using blocks is that they are re-definable. For example, if there is a change in the relevant windows, then we must deal with all of them one by one. However, if we make them blocks, then as soon as we change the definition of the block, all of the blocks that were inserted into the drawing will change automatically.

Use of blocks is not limited to these. We can create our own libraries by making them blocks. By this way, our works in the drawings will be fastened.
For example, if you are using fasteners in your drawings, instead of drawing them of opening another drawing and copying and pasting it every time, you can insert them from your own libraries. After giving this general information about blocks, now let’s examine them in detail.

In order to define a block inside the drawing, we will use the “BLOCK” command.

When we execute the command block definition window as shown in Fig. 1 will appear. In this window, “Name” is the name we want to assign to the block. For example, if our block is a fastener, it may be something like M12×25. “Base point” field is for the insertion point of our block. Insertion point will be our reference point while inserting the block.

Fig.1 Block definition window.

And the “Objects” field is for selecting the entities that will be included in the block. The three number of settings included in this field is about what to be done with the entities after creating the block. If “Retain” option is selected, then as soon as we create the block, the entities are left as they were. If “Convert to block” is selected, then it converts the selected entities into block. If “Delete” is selected, then it erases the entities selected from the drawing. Settings inside the “Preview icon” field is related to if there will be a preview while inserting the block into the drawing. Preview is extremely useful for distinguishing blocks from each other. By this way, we can define our own blocks by naming first and then selecting the relevant entities and finally, by selecting the insertion point.

Re-definition of the block we have created (modifying):

By the help of this command, we can make the necessary changes inside a block that we have created before. This change that we have made will affect all of the blocks inserted in the drawing. As in the example of windows that I have explained above, if we modify one of them, due to the fact that we are changing the definition of the block, all of the windows in the drawing will be modified accordingly. When we execute the command, it will prompt us to select a block. When we select the block, “Reference Edit” window as shown in Fig. 2 will open up.

Fig. 2-Reference edit window.

If the block that we select is already defined in another block, it will be seen in a hierarchical orientation as seen in the figure. Let’s select the block that we would like to modify and confirm by pressing OK button. After completing the selection operation, now we have to select the entities, which we want to modify, inside the block. After completing this selection as well, then the Refedit toolbar will open up in the screen as shown in Fig. 3.

Fig. 3

1. To add an external object into the definition of the block.
2. To remove an object from the definition of the block.
3. To exit the block modification without making any changes.
4. To save the changes that we have made and exit block modification.

We can make the changes that we want inside the block after the Refedit toolbar opens up. After making the changes, in order for these changes to take effect and saved inside the definition of the block, it is enough to press 4th button.

I will continue writing articles about blocks.

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• Blocks IV - Count your blocks with EATTEXT command
• Blocks II - Preparing symbol libraries with WBLOCK command
• Preparing a block library by using TOOLPALETTE feature
• Dynamic Blocks and LOOKUP parameter

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Autocad, Blocks