Hide/Show parts of a forum post - How?

Continuing the discussion from Make several components unique to one definition - in Ruby:

I’d really like to know how @DanRathbun did this:

Select the text that you want to “hide” and then click the “gear” icon above, then choose “Hide Details”

[details=OK, Testing this:]
Will this text be hidden/showable with the down arrow?[/details]

Cool! Thanks!

1 Like

[details=Hidden quote from Steve …][quote=“sjdorst, post:1, topic:37170”]
I’d really like to know how @DanRathbun did this

There are things that refuse to be hidden. I tried to hide a GIF image in another thread and although it rendered like it was going to work in the post preview pane, after posting the image just rendered below the hidden details block. (Clicking on the details caption didn’t do anything much.)