Update 12 Nov 2018: I printed this out on my Prusa Mk3, and discovered my sizes were all wrong for that printer. Due to the tolerances involved to press onto the hose and fit tightly - but not too tightly, you may have to print this out, test fit it, and then scale it to get the right fit. I've played around with it some but haven't come up with a size that works between my Prusa and my Monoprice Select Mini with good results.

I've got the basic Shimano SM-DISC-BP bleed kit that I use with syringes from another bleed kit, but when I was at the bike shop, I saw the TL-BT03-S bleed kit which includes a clever little plastic tool that helps lock the hose on the bleed nipple. Since I already had the basic funnel, I didn't need to get a complete extra set, so I set out to replicate the hose lock tool, and that's what we have here.

The tool is sized for use with 1/4" OD plastic tubing, and the hole is sized to get a good tight fit with my printer - you may need to scale it if your printer is more or less accurate than mine. One one side, there is a "T" recessed into the face of the part, and this indicates that the hole is very slightly tapered on this side. The opposite side should be a tighter fit, so you'll likely want to insert the hose on the "T" tapered side. If your printer gets any elephant foot (bulges slightly on the first layers) then you'll also want to clean that up with a file.

Once it's on the hose, it's quite easy to use.

1. Remove the rubber cap on the bleed nipple, if you have one. I like to remove it completely as this allows the hose to go over just a little bit further and helps lock it in place.
2. Press the hose onto the bleed nipple as you would normally
3. Push the lock tool down the hose until it's over the bleed nipple - see the photos.
4. Bleed the brakes as you would normally, using a 7mm combination wrench to open and close the bleed nipple as necessary.
5. Once you're done with the bleed, push the lock tool away from the caliper and you can remove the hose.
6. Reinstall the rubber cap on the bleed nipple.

I find that I get the best results with the tapered side (containing the "T") facing towards the brake caliper, but try it and see how it works for you.