How to get rid of this?

[syunysi]

I accidentally deleted the application folder, but have now put it back, however, after deleting the application folder, "a few vertical lines" has replaced the location on dock (picture attached). Could someone please help?

 

[ergdegdeg]

That's just the separator between apps and stacks/folders in the dock. That's always been there and you can't remove it. Your app stack is below your document stack.

 

[Raid]

I think you can go into the terminal (in Applications>Utilities) and type this:
killall Dock.

That should restart your dock.

 

[Gregg2]

Sounds like all is well, thus no need to reset the Dock.