It's bar that has little slots that you snap a clip into it.
I've done all the above include this. They call it Adjustable Pilaster Standards and shelf clips. It works great. If you dado them in like I do, it's just as much work to install as a fixed dado'd shelf slot. After installing a few, then I started numbering the slots, because at 1/2 inch increments, customers had trouble trying to get a shelf leveled. On kitchen shelves... well canned goods and such add up weight fast. On double door cabinets, I like to add a support to the rear panel and to the back of face center frame piece other wise those sag eventually. Asthetically, most of my past customers didn't want to see this type of support. To me, on my own stuff or my own preference, I always thought this type doesn't look as finished. Behind closed doors right? I know.
I can drill a series of holes and use dowels or real shelf hardware
or I can mount standards standards in grooves cut in the cabinet side
or add standards and leave them standing proud
or??????
Most of the time I do drilled with peg supports. I prefer this method. It is really easy once you get a system/technique. Mine? I take a piece of hardboard and drill holes in it to use as a template. I use 1 1/4" spacing. I don't know why that spacing = it's just what I was taught and no-one ever told me any different. I usually start holes about 6 1/2" for the bottom base dado and stop about 6 1/2" to 7" from the top (depending the the height of the cabinet.) I tape over where to holes are going to be drilled with blue painter's tape. I use a template to drill the holes, not just for the spacing, but because veneer or mdf seem to lift up and tear out if you don't. On double door'ed cabinets, again, I drill holes into the back panel/back spline and into the back of the front face center frame post.
Yes I tried dowels way back when. For adjustments (and often does someone decide to adjust a shelf?), after sitting a while with weight, if you "have" to move that shelf, then peg does deform a bit and I usually had to remove it with a pair of pliers and replace it.
Fixed shelf:
Supported standards, to me don't look as finished, unless you make them decorative and in context to the trim work. I've used them. I don't personally prefer them in a cabinet. I don't mention that option to a customer unless it goes with a look they're after.
Dado'ed, dado/doweled or mortised. (not mentioned, but just as fixed as the above supported fixed standard.) I think these look finished for a fixed self. But then it "is" fixed/nonadjustable.
