My brakes have just started making a scrubbing sound when I apply them pretty stern. It only seems to be coming from one, and it will stop if I apply them stern, and then let up and reapply them.

I just had the brakes replaced on Truck and Trailer 3 months ago, and have not had any problems or noise until now.

Any suggestions on what to check for this?

could be a simple thing like sand or gravel in your drum.
Only way to find out is take off your wheel

first check your brake stroke.

jack it up and check wheel bearing endplay.

check for dust shield to drum contact.

but, you likely will pull the drum, dump out debris, scuff the lining and drum surfaces, then re-assemble to make it go away... maybe even re-line.

Thanks, found the sand and got rid of it. smooth sailing now, or should I say braking now.

Assuming the brake shoe linings are not worn out, I would just remove the dust shields (AKA "backing plates"), then back off the slack adjusters and use an air blow gun to blow out any foreign material that's caught in there.

Sure a lot easier than pulling the hub/drum, replacing the seal etc., just to get the crap out of the brake shoe - drum interface area.

Note: when using compressed air around brakes, always use respiratory protection, as brake dust is hazardous to your health.

After blowing out the dirt, be sure to properly readjust the brakes and re install the dust shields.

obviously, you do not live in the rust belt ;0)

most outboard drums can be removed as quickly as a dust shield anyhow.

... most any service manual will specifically tell you DO NOT use compressed air to remove brake dust, they will usually recommend a damp cloth or brake clean.

Yes I do. And if it's rusty drums that are causing the noise, a few normal stops will allow the brake shoes to "sandpaper" the rust off the drums.

And many trucks & trailers have Dayton wheels.
The original post did not specify.

That's why I stated the following:
Note: when using compressed air around brakes, always use respiratory protection, as brake dust is hazardous to your health.

Why do all that extra work when you could do it the easy way and get the same result?

my reference to rust was the fact that around here practically NO dust shields come off without dealing with broken bolts.

in today's world, unless specified otherwise, i assume outboard...

we all know about asbestos, and the fact that when the fibers become airborne, they do not settle to the ground for a long time..., that creates a hazard for other techs in the shop, or your buddy that's helping you, or you (after you've removed the respirator).

IMO