Greetings -

Because our cat won't take no for an answer, we need to reinforce the
catflap against escape. The simplest solution is a slide in 'guillotine'
panel which covers the whole assembly (insert jokes about sharpened edge,
baited with tuna etc).

I have various types of stout thin board, that's not a problem. But I need
some J-Channel to slide it in and out of. Something like 10-20mm wide at
the back, and 5-10mm wide at the front, and able to accept a 3-4mm board
sliding in. Two lengths of 250mm would be adequate, sturdy plastic or
aluminium would be ideal.

I've seen similar stuff on the back of self assembly furniture, to hold the
hardboard back on. Common-sense says there's probably some way to scavenge
or convert it - cut-down electrical trunking, alloy channel for fixing
greehouse glass or summink?

Ideas very welcome...!