I assemble the couplers in the box, and set them like they would be if the spring was installed. I use my hobby knife and push the blade into the end of the spring, then set the spring into the little pocket formed by the coupler halves. I compress the spring with my knife, then push the spring off the knife with a small screw driver. Then, I gently place the lid on the box and give it a quick bump with the soldering iron to seal it.
I have basically been doing the same thing now for a few years taking the point of the number 11 blade and slipping it in between the spring coils. I have never had to use a soldering iron finding that the snap fit on the box lid has been enough for me. And even with my old eyes and ten thumbs I'm good for about thirty to forty 1015/16 assemblies an hour.
This only works for the 1015/1016s, as all the other MT boxes do not have a snap fit lid. Even with 1015s being almost "universal," I still find I need other couplers for quite a few of my locos or projects.
