Strange pneumatic valve I ran into last night
 

I was troubleshooting a clamping system this morning and notice that the 3
position air valve didn't bleed pressure off even though it was clearly
marked as one that bleed A and B when centered.

I traced things out to a manifold block that seems to be able to balance out
pressure on both sides of the clamping cylinder when the pneumatic valve is
centered.

It is rather impressive how somewhere between 0 and 87 psi can immobilize a
2" balanced piston cylinder in mid position. I ran a few calculations and
understand what is going on but my question is what to they call the valve
that is locking the cylinder in position?

Thanks,

Wes