Editing diagram and all of a sudden all lines infinite?

I am a newbie and I must have fat fingered something, but as I was editing my diagram all of a sudden all the lines in the diagram extend off the screen and can't be trimmed. I was in the process of adding a new layer when it happened, but removing the layer didn't fix it. I tried removing my .config/LibreCAD folder and it didn't help, so I assume it must be embedded in the file. What did I click? Thanks for your help.

Ah ha, I found it, I clicked this pound sign I guess, not sure what that mode is for exactly.

On Thu, 1 Apr 2021 15:58:34 -0700 (MST)
"nick26 [via LibreCAD]" <[hidden email]> wrote:

> I am a newbie and I must have fat fingered something, but as I was
> editing my diagram all of a sudden all the lines in the diagram
> extend off the screen and can't be trimmed.

Would you by any chance being putting your drawing into Layer 0(zero)
which is the "Construction Layer"  and is there by default?

BTDT. <vbg>


> I was in the process of
> adding a new layer when it happened,

IME, I've found that after the first step of "save as", the next step
is to define a layer or few.

 but removing the layer didn't