Extending & Trimming - why does this happen?

I had the drawing open which you had a look at yesterday. Went to the design center, in the design center went to folders, select the drawing drive, find the drawing where we create our standards in, it has a "+" at the left of the drawing name. Make the "+" a "-" there it gives you options of Blocks, Detail View Style, Dimstyles, Layers, Xrefs etc. Select Blocks, select the block drawing, dragged it from the design center to the new drawing which you had a look at and made the modification to fit in the assembly in there. Hope this makes sense.

That all appears normal, but you say that doing that then changed the way the block looked in the standards file as well?

I think i start to understand. When i used the standard drawing block, copy it in to a current drawing. Thus, ACAD has taken that block into your current drawing itself and made it part of it. So when you do modification to the block, it will only change the block in the currently used drawing. Not the standard, even if the preview indicates the change, the change has not happen in the standard drawing, only in the current drawing. In the standard drawing the block remains as is, cause the block is read as part of the standard drawing. Making my explanation bit simple: You have two cars one a Ford the other a Chev. You use the Fords Side door, make a copy, put it on the Chev, modify it. The Fords Door remains as is, cause it is part of the Ford. The modification on the Chev stays with the chev. Did i get to understand the block yet?

The block in the standards file will not change even if you drag/drop it into a working drawing via Design Center then edit it. It is not a two way street. The edits made to the block do not flow back in the other direction.

I'll check the tutorials out, there is something that doesn't make sense as RobDraw explained about blocks and xrefs. Using the above drawings as ReMark explained, i opened Design Center/select the standard sheet/ blocks; Dimstyles, layers etc. Under blocks i find the detail i was looking for, under xrefs its empty. Dragged the correct detail over to the drawing, modify to see what will happen and the "block/xref" in the standard sheet has also changed. Is it an xref or a block?

It's obviously a block.

What do you mean by sheet? Another layout in the file or a different file altogether?

(Please be careful with terminology as it will only serve to confuse things, if you do not use concise terms.)

If you would like to start a discussion about blocks vs. XREFs, I'd suggest starting a new thread.

That is correct, now you just need to work out in your mind how making hundreds of elements into a block and then copying the block a hundred times in the same drawing, makes the drawing file smaller than if you copied the loose elements a hundred times.

Ok. I have check the tutorial, it was very helpful to get the understanding between block, wblock and dynamic block.

LOL, my mind runs at 100 lines per nanoseconds. Thank you all. Damn it feels good to see the sun at the end of the storm.

Ok RobDraw, not a bad idea you've got there. Maybe start the thread in beginners area, or on AutoCAD LT?