If you haven’t looked at your TF2 manual, take a peek at Ubermanuals.com (where you can also find wayward manuals for vacuum cleaners).

Always keep this in mind when Maintaining your Upgrade of the SG:
When Ultra-Sapper device is affixed to the top section
of the sentry device, remove red and green
wire and tune dial (bludgeon device with [...]

This is one of my favorite new DoD:S achievements; the Double Cross. Tip: you must be tenacious with this one - don’t let a smoking projectile pass you by without picking it up.
You must be fearless!!
Also, if you want to know a great place to pick up this achieve very naturally, try [...]

All right, I know I’m slow - but am I the only one who didn’t know the Scout could do this?

For the record, I do know how to turn my Engy buildings before placing them, thankyouverymuch.