hello ,, to the Garden city,, of ozz, if it has a screw head on it, its a screw,, it should turn anti clockwise. to the left, but you might not be useing the right fit screwdriver on it, try putting the screwdriver into the slot, and giveing it a light tap" down with a little hammer. and it might help it turn, or see if you can get a small vicegrips. to grip it and try turn it. also spray some wd40 oil on it,
m,,,, IRELAND, January 2012