Hi gang -
Everyone's favourite game - I can't search for them on Ebay if I don't know what they're called....
L-shaped chrome or brassed clips, 13mm long side, 5mm short side. One screwhole on long side, plus little spikes to grip the wood. You screw them to the side of a flush-glazed picture, with the little 5mm lip reaching round to hold the glass in place.
I never doubt the power of the hive mind - thanks in advance :o)
Steve