As always, I start by taking a good look at the real item. The main body of each rein is laced with a long, narrow strip of leather forming a row of sideways V's that point away from the bit toward the rider.
This is a small detail, but it's one that never varies. I hate to see an otherwise lovely model bridle ruined by backwards laced reins. You will never see that in the real world...
So be sure that those V's point back at your rider!Notice also that the laced portion of the rein makes up somewhat less than half its total length. The first third of the rein (give or take) may be either plain, flat leather or raised to match the bridle's brow and nosebands. Either way, it will not be laced.When viewed on the horse, the beginning of the laced section typically falls somewhere around the midpoint of the horse's neck.
This is a rule of thumb, not an absolute.
Depending on the horse's head position and length of neck, the beginning of the laced section may be further forward...
or further back.
The main thing is not to get it too close to the bit. I see a fair amount of hobby bridles with reins that are laced nearly their entire length. That's way too much work and looks funny to boot. Remember the laced section is there to provide the rider with better grip. You only need to lace the parts of the rein that might conceivably be held by a rider.
That's it for today--tomorrow we'll build some reins!