I put plastic panels btwn the buck pens. Cuts down on peeing contests and they're easier to clean. They're between the pens - not actually dividers.
Have also put plastic panels between a couple of doe pens as one of the does got very protective of her first litter and wanted to fight with her neighbors as they checked things out. Took them out after the litter was weaned and she was much calmer with her second litter. Again, these are attached between (outside) the pens and not actually used as dividers.
I've used sheet metal before but like the plastic as it cleans up better.