I hot glue the tile and the caps down. When everything is set, I have those long hot glue strands hanging everywhere. I have to be sure and grab them and pull them off or else they mess up the grout.
I use unsanded grout made in very small batches. I pour it onto the area and spread it with a rubber kitchen spatula because the space is so small.
I clean the grout off and let it set for a couple of days. This time I coated the caps and grout with polyurethane twice. Hopefully, the weather won't rust the caps, but if that happens, it's OK. We will just call it rustic.
The whole project cost $1 for the glue sticks and $9 for the poly-urethane I got the wheels from the garage of a friend. The 16 inch tile from another friend, and the paint from yet another friend. The moral to this story is: Ask your friends if they have leftover paint, tile or other small building materials. People who have garages or sheds almost always have some leftover materials from their own projects. :-)