What the builders left behind.....

They are though

When used with timber frame even a 6" nail knocked in is enough to key brickwork.

They only need absorb a little shear force

Have you had a look at the Screwfix example? Having used some in the past I can tell you they are not particularly substantial, the vertical pieces need to be able to give a little to accommodate unevenness in the existing wall and as a result the bracket part has to be flexible enough to be held level. As Jim kindly pointed out they are off cuts of wall starters.

Richard

I cannot see the pictures, but way back in the mists of my memory, one company also made facia covers for their brackets out of springy metal that hid the bare metal underneath. You could get them in many colours. Brian

Yes, I did check your link, but these are not remotely the same, I'm afraid - aside from which there were no new walls built. This was just a re-roofing job.

Roofing job you say? When your new tiles (or slates) arrived on pallets, they were probably lashed together using straps or bandings. Could this be a clasp from one of those straps?

what was the roof roofed with? Could be slate hangers

Well, not much came of that excercise.

Nobody nose...

The ones in the picture are not stainless steel or galvanised, so definately not wall starters or timber-framing cladding

Concrete tiles (Marley).

I think they're parts of a drawer runner. They're possibly not load bearing, they just hold bearings or rollers in place between two structural runners, one attached to the frame and one to the drawer.

Or, could they be designed as an accessory for a wall starter like:

I don't know why these drawer runners and wall-starters are even being suggested, given it was a new roof job didn't involve either!

Fair point.

Pretty conventional in the main. Replacing old red clay tiles with new grey concrete ones, together with a 'dry ridge and hip system' for the angled bits.

Seems the most likely suggestion thus far.

Racking offcuts,is one end cleaner (recent cut)or dug up during work.

Perfectly strong enough for shelf supports,you find such stuff inside metal cabinets, If I get time I might,take a photo.

because its taken you two days to tell us that And, looking at te state, its not clear that if the roof was done recently those are anything to do with it

Somebody had used these drawer runner parts to bodge something on the old roof.