With the D-nail quarts pieces they fit around the actual domeless nail and sit on a platform below them so that they dont wobble or need to be screwed into place like with the TI ones.
This also helps because instead of heating the post it heats the actual nail and walls so it would make it slightly more effecient and probably tax your coil/box a little less.
Heres what they look like if you didnt see on the first page.
^^^ You slide the coil around the outside of the top part of the nail and it rests on that little ledge. On a normal domeless quartx this would be hard and all of the torque from the coils cord would be pullin on one side of the nail and easily break it because it is floating not resting. Check out some of bubblemans shit on youtube he uses his enail alot and makes very good videos.
greenghost, theres a link to the REDDIT DIY ENAIL page on the first page of this thread, actually in my first post. But if you want more detailed info id just look up different PID controllers and the whole PID meaning/function. Unless youre a wiz at math itll make your head spin. Its not super complicated when its broken down because all youre doing is trying to find a constant and consistent "frequency" that will cause your coil to hover at the exact temp you want it.
Kind of like with a helicopter. You gotta give it enough gas to counteract gravity while not holding it too high as to continue to rise. Except they make it into a long equation with a bunch of symbols and numbers and i failed math in HS so alot good thatll do me.