installing door knocker on upvc door?

i want to install a door knocker to my upvc door.........what's the recommended largest size screw that can be used please
rosemary lambert, February 2010


done
you need to use the size thats fits the width of the fixing holes.probably 6 or 8mill.length wise 15mill to 20 mill will be ample.carefully drill a 2/3mill wide pilot hole 1st,then put your srews in

pete d curtin, March 2010