Take it out using a wide chisel or flat scraper like a wallpaper scraper, start in the middle and ease the bead upwards, this effectivley shortens the beads and releases the mitre joints from each other.
Pinned means nailed back into place but with 'panel pins' not nails, glue should not be necessary, i would also tosh the nails in to stop the bead easing back out.
Now your going to ask what tosh means?..........It means putting the nails in at an angle rather than vertical, it stops the nail being pulled out by the bead IF the bead still wants to bow up
if your scared of hitting the glass when you come to replace,
then here's a little trick.
make sure you slide the hammer on the glass to strike the pins.
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local