It's kind of difficult to explain, but on one end, (the one without the screw in the hinged part), the slidy bit (that pushes out the lug that fits in the hole at the front) can actually be pushed back in away from the edge of the deflector and this releases the hinged part so you can fold it back on itself.
If you understand that I congratulate you!
MCC Astro Black, collected 21 July

, all is well (alarm has not false alarmed since 15 December 2004!)