To go with our 19"/20" 4 1/4" wide C section sports/racing mudguards (Items 0305R/0307) is this fabricated bracket that locates under the mudguard to allow two mudguard struts to attach the mudguard to the frame (or similar).
The bracket is lasercut and then pressed to the same form as the C section mudguard, so is a good close fit under the mudguard, as per the second photograph.
This bracket is most suitable for fitting under rear mudguards so that a tubular strut can be ran down to the rear axle spindle of your frame - it then well supporting a bum pad or similar. It is manufactured from 0.112"/2.8mm steel so is good and strong for this purpose - much easier than having to fabricate one yourself!
Update 2022: We can now offer a second version of this bracket - which has longer extending struts - see also Item 1081