You can make a split Y (like winners choice) or a floating yolk (like Hoyt standard strings).
The Floating yolk gives you the same thickness on the V part as the main | of the string. This string is made in two parts with the V at the top being 14" on my Hoyt. If the label on your bow says something like 38" for this cable then the | part would be 31" and the V part 14" (when folded = 7") and before attaching to the bow you would assemble both parts and put the end loops of the V part on the same post so you can measure the overall length.
The loop on the | where the V fits through should not be served, but be kept 'soft' ie just the string material.
To make the 14" cable I use an arten jig with a crossbow adapter fitted. It is probably the cheapest way.
The Split yolk can be done by wrapping a Y shape from one post out to 2 in two parts. Say if you want 20 strands, spool out half your string so you end up with the two loose ends at one of the V posts and then do the same with the other half so the two loose ends end up at the opposite V post. Use the GRIV serving method (shown in another thread) to serve the small loops at the V end. You can now go to the | end and serve the single loop in the normal manner.
The advantage of this is that it is easier to tune individual sides of the Y but if its not done correctly you can induce cam lean.
No doubt there are many other methods out there - this works for me
