On Mon, 4 Jan 2010 12:21:46 -0800 (PST), Plumber Bob wrote:

It's not at all intuitive but every plumber on the planet knows these
Symmons faucets inside and out so just ask one when/if you get stuck.

I'm not a plumber so it wasn't known to me.

Your suggestion to screw the lag bolt worked perfectly.

I had to slide a circular weight onto the lag bolt and smack the underside
like a dent puller until the plastic came out of the Symmons faucet.