I awoke this morning feeling ready, so I took the slider off. The 'nub' turns out to be a nipple, I think; a lubrication fitting. It was threaded into the green plastic end-piece, and I had to remove it to get the red plastic end-piece off. As I wrote earlier, it has a tiny ball on the outer end. It is a threaded (M3?), hollow tube, with the nub outer portion being a 4mm hex head.
Inside the slider there was a little, very little, swarf. But, there was a good film of light, relatively clean, oil on everything. I'm pretty sure the nub is a lubrication fitting. So, did they just forget to take it off after assembly and oiling?
I was so careful. I disassembled the slider over a large bowl, hopefully to catch any jumping, flying parts. But, in trying to pry loose the first bearing retainer wire, boom, 20, or so, ball bearings fell out, bounced off the bottom of the bowl, leapt onto the granite counter, and rolled, in all directions, off the edge, and jumped to the floor. From there they clickity-bounced and skittered into the best hiding places they could find. If there should be 44 bearings per side, or 88 total, I'm now 6 ball bearings short; I only found 82.
So, I searched this thread and found a link to AliExpress linear guide slider MGW15H. Just to check I also searched AMZ for "MGW15H." I was surprised that a whole bunch (similar, anyway) showed up, and even more surprised than many of them seem to come with the 'nub.' In the image of this one it looks more like a grease zerk:
https://www.amazon.com/ThgivingStor...9/ref=pd_day0_d_sccl_4_28/144-8669635-3706554
I measured the steel balls with my digital calipers and came up with 1/8 (0.125) inch exactly, so I think I'll order a pack of 100 (440C stainless, grade 25) from Uxcell-AMZ and have them delivered tomorrow.
Has anyone mounted their Toohr/Ketiped to a flat, heavy board, like a thick HDPE cutting board?