I think Susan asked about putting leftover trimmed brisket fat on top of other leaner cuts to keep them moist.
At a BBQ demonstration that I saw by the KC Rib Doctor (Guy Simpson), he talked about how fat cut from the top of a brisket when fried in a skillet will mostly burn, it doesn't render nearly as much as the pork fat in a second skillet did. Pork fat generally renders pretty well, but beef fat doesn't, which is why it seems to be a pretty good idea to keep that fat cap on a brisket fairly trim while you can get away (or even prefer) not to trim most fat from a pork shoulder.
I think that's why more people bard their lean cuts of meat with bacon or pork fat (this is what fat nets are for, if you've ever seen "Iron Chef"). I've done it to game hens and venison tenderloins and the results were great. You could also lard (as opposed to bard) a piece by actually putting lard or slivers of pork fat into shallow holes pierced into the meat, but I've never done that personally.