OK this is not yer B&Q probably - I have some ogf their products and they don't quite do.

What I am looking for is rubber extrusion, P in cross section and bigger and with more flat section than B&Q product.

This is to hold water back not wind, so it has to be several feet in length, and big enought to accommodate being pressed against pebble dash. Stapled to a board that will be held in place by bungy cord. Effectively a dam across a porch. Floods!
The dam is done at present but I can do better with the right material.

Anyone any ideas? Yea yea taking the P joke assumed and found funny - almost.

Area of Gloucester if retail outlets. Double glazing firms are being investigated. Weekend looks like rain - so need soon.