This is a shelf bracket I made to fit over the picture rail sold by Wickes (a builder's merchants in UK). I think they also sell the same picture rail in B&Q although I have not tested them for compatibility. The bracket measures 122.5mm x 122.5mm and is 35mm wide. It features a quatrefoil design which has different symbolic meanings in different cultures. It is intended to look like a wood carving (once painted) and is mostly suitable for Victorian style interiors. There will be a 14mm gap between the top of the picture rail and the bottom of the shelf, to allow picture hooks to be installed when the shelf is in place. There is a 5mm hole provided for a screw which is intended to go through the top of the shelf, through the bracket and into the picture rail. I would recommend spacing these around 600mm apart if using 18mm thick shelves. For best structural performance, print flat and use supports. The face printed on top of the support will likely have a rough texture, so be mindful of the orientation and use the mirror tool in your slicer if you want the rough side facing one way or the other. I've printed this with Sunlu PLA Meta on a Ender 3 v2, with good results at 75 mm/s speed and 185C/55C temps