A block in Autocad is a collection of all of the line and arc entities that create an object, 'moulded' together to make one selectable object. Selecting one particular entity (such as a midpoint of a line for example) will select all objects contained within the block. They can be moved, rotated, mirrored etc and will always be treated by Autocad as one whole object.
Why use Blocks?
Blocks are an invaluable way of quickly arranging complex pieces of a drawing. Selecting the object is a breeze, it is no longer neccessary to painstakingly select each indivdual line. They also prevent accidental modification of parts of the object, as they cannot be modified unless the whole block has been exploded. Blocks also make it easy to duplicate the same object throughout a drawing, and as Autocad recognises that each copy of a block is identical to the previous, the memory & processing time required byAutocad is reduced.
The most impressive feature of blocks is that if a block detail has to be amended, simply changing the detail and 'redefining' the block applies the changes to EVERY instance of the block in the drawing!
Blocks are an invaluable way of quickly arranging complex pieces of a drawing. Selecting the object is a breeze, it is no longer neccessary to painstakingly select each indivdual line. They also prevent accidental modification of parts of the object, as they cannot be modified unless the whole block has been exploded. Blocks also make it easy to duplicate the same object throughout a drawing, and as Autocad recognises that each copy of a block is identical to the previous, the memory & processing time required byAutocad is reduced.
The most impressive feature of blocks is that if a block detail has to be amended, simply changing the detail and 'redefining' the block applies the changes to EVERY instance of the block in the drawing!
Here are the two good websites with a huge blocks library of 2D and 3D objects:
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