A few people have mentioned Jett Sett recently as a solution for
holding pieces so I had to jump in with my two cents - because it is
Jett BASIC and not Jett SETT that might be the better option. Jett
Sett is a ceramic-impregnated material that arrives in pellet form
and is intended to melt together and be formable into any sort of
holding shape without stickiness (the key issue). Jett Basic arrives
in white pellets but melts into a clear, completely unified mass that
is also formable into any shape.
Jett Basic IS sticky so it does just what I want - conforms exactly
to the object I’m holding without having to load up a lot of bulk
around it. Moreover, it sticks completely to itself, forming a thick,
malleable putty with no gaps or bits that flake off. It doesn’t leave
any residue in the heating pot since you can swirl a chunk around in
the water and it picks up every bit that might be floating around.
And it dries HARD, so it gives great support. I use it for setting
enamels & stones and hold it steady by squishing it into a vise. This
is the stuff you see Blaine Lewis use in his bezel setting video, btw
(no vested interest here.)
The only downside to Basic I’ve seen is that it sticks to anything
plastic so you have to be careful about what it touches. It doesn’t
stick to skin though, so it’s not a pain to use.
On the other hand: the fact that Jett Sett ISN’T sticky makes it
difficult to hold objects tightly. Since it doesn’t stick to metal,
it carries a coating of water that inhibits good contact. Then, since
the contact is poor you have to load up bulk around the piece, making
access more difficult. Moreover, it doesn’t stick to itself very well
so even after kneading to make it into a solid mass, bits flake off
and crevices open up as it is drying. This makes it poor for holding
small objects - they just split pieces off and pop out. It is also a
god awful mess to use and to clean up - It leaves powdery flakes all
over the bench and a gunky sludge in the pot because the smaller
particles are impossible to ‘catch’ and incorporate into a larger
mass. After all, it isn’t sticky.
Sooooo, I don’t know if people really meant Jett Sett or Jett Basic
when they mentioned it, but for the applications in question (holding
small pieces for drilling, etc,) I would recommend Jett Basic. FWIW,
I’m trying to salvage some utility out of the Jett Sett by making
shallow dapping punches out of it. I’ll let you know what happens.
Betcha five bucks it shatters to bits after 3 uses. No offense to the
manufacturer, of course 
A blanket disclaimer - these are my experiences and others may see
it differently. Will that save me from a deluge of ‘you used it
wrong’ emails?
Linda