How to Edit a Block in AutoCAD and Explode It

A block in AutoCAD is one definition with any number of references placed in the drawing. Editing a block means changing that definition, and every reference updates with it. Exploding a block is different: it breaks one reference back into loose lines and leaves the definition alone. These steps use AutoCAD. BricsCAD has the same BEDIT, REFEDIT and EXPLODE commands.

Edit a block in AutoCAD with the Block Editor (BEDIT)

Type BEDIT, or double-click the block.
In the Edit Block Definition dialog, pick the block name and click OK. The block opens on its own, with its base point at the origin.
Change what you need with the usual commands: move, stretch, erase or draw.
Type BCLOSE and choose to save the changes.

Every reference to that block in the drawing now shows the new version. The base point stays at 0,0 in the editor, so if you move the geometry away from it, all the references shift by the same amount.

Edit a block in place with REFEDIT

When you need to see the surrounding drawing while you edit, use REFEDIT or right-click the block and choose Edit Block In-place. Select the block, confirm it in the Reference Edit dialog and the rest of the drawing fades back. Edit the block where it sits, then type REFCLOSE and save. The result is the same as BEDIT: the definition changes and so do all its references.

To change only one copy, give it a definition of its own. Explode that copy, then turn the lines into a new block with BLOCK under a different name. The other copies keep the original.

How to explode a block in AutoCAD

Type EXPLODE and select the block. The reference becomes the objects it was made of, on the layers they had inside the definition. Objects drawn on layer 0 inside the block go back to layer 0. EXPLODE works one level at a time, so a block that holds other blocks breaks into those blocks first. Run it again to get down to lines and arcs.

Explode a block in AutoCAD with XPLODE

XPLODE explodes like EXPLODE but lets you choose the layer, colour, linetype and lineweight of the resulting objects, or have them inherit the properties of the parent block. Pick the blocks, choose Individually or Globally, then the property to set, and finish with the Explode option. It is handy when blocks from different sources should all end up on one layer of your standard.

Why an AutoCAD block will not explode

The block is set as not explodable. The Allow exploding option was cleared when it was defined. Open it with BEDIT, click an empty spot so nothing is selected, set Allow exploding to Yes in the Properties palette and save with BCLOSE.
It was placed with MINSERT. A block array made with MINSERT cannot be exploded. Insert the block again with INSERT and make the copies with ARRAY instead.
It is an external reference. An xref is not a block in the drawing. Bind it from the External References palette first, and it becomes a block you can explode.
It sits on a locked layer. EXPLODE skips objects on locked layers. Unlock the layer and try again.
It did explode, one level. With nested blocks the first EXPLODE often looks as if nothing happened, because the pieces are still blocks. Run it again.

Editing downloaded blocks in AutoCAD

Every Cadtorial file holds its views as named blocks, such as CT_SOFA_3_SEAT_PLAN and CT_SOFA_3_SEAT_ELEV for the 3-seat sofa. If you insert the whole file, AutoCAD wraps both views in one block named after the file. Explode that once and you have the plan and the elevation as two separate blocks. Explode one of them again only if you want loose lines. To bring a single view, drag it from DesignCenter as described in how to insert a CAD block.

The symbol sheets in CAD symbols go one level deeper. Each symbol is its own sub-block inside the sheet, for example CT_ELECTRICAL_SYMBOLS_IEC_SOCKET. Explode the sheet once and every symbol becomes a block you can copy around the plan and edit with BEDIT, so changing the socket once changes it everywhere.

All our blocks are saved as explodable, with no attributes and no dynamic parameters, and the lines are on named layers set to BYLAYER. That means exploded geometry keeps layers such as A-FURN or E-POWR-SYMB instead of falling onto layer 0. One thing to watch: if you edit a view with BEDIT and later insert the same file again, AutoCAD keeps the definition already in your drawing. Rename your edited version with RENAME if you want to keep both. The licence terms for edited blocks are on the blocks license page.