Gear Auto-extend
It's a bit of a pain, really. Unless the pin has been removed, you can pull up the "override" knob and push in the pin to lock it up.
Otherwise, the pesky gear will drop as soon as you go below the limiting speed, and as soon as the engine fails.
We "lost" our first Arrow when the engine went BANG over the Solent, and the gear dropped immediately. P1 didn't realise (bit preoccupied with other things) and didn't quite make it to shore. With the gear up, he would have done.
There are all sorts of strange requirements which basically mean you can't change what's there.
If you lock the override "up", then the gear will retract when you tell it to on takeoff. Otherwise it'll stay down (or half-down) while you slog up to altitude.
Our "crossing water" check includes "gear override up and locked".