How to Make Heavy Stuff Out of Gluons

Gluons have energy inside them, even though they are massless. Most of the mass of a proton doesn't come from the quarks that make it up. If you could get a bunch of photons and store them inside something, even if they're mass lists, they would add to the mass of that object. You can make it out of massless stuff as long as you concentrate some energy in there.