I ordered a yhm soild quad rail free float rail from operation parts. It was closeout that came with rail and fold down gasblock/sight. My question is do I need to oder a special wrench to Install?

Some people will tell you that you can tighten the jam nut with a screw driver and hammer.  Well, I suppose you can, but I'd sure like to know how many jam nuts YHM sells to people who screw up the original jam nut.  Must be a lot since they do sell them as an extra part.  Any mil-spec wrench  with free float studs will fit the barrel nut but to tighten the jam nut you really should use their tool IMO.  However, if your handguard has the locking screws on the side then the jam nut is for pretty much for show anyway and a strap wrench will tighten it plenty.  On the new style YHM handguard with the locking bolts on the side of the handguard, I just snug up the barrel nut with the wrench and give it a tap with my palm for good measure.  I've never had any come loose.  I guess you could just tap it with a hammer and screw driver but don't slip or you'll put a nice booger on your jam nut.

I've put many a barrel nut on with a DPMS 3pin 1/2" drive socket wrench or PRI 5pin which will more evenly distribute torque and accurate reading to your wrench. If you feel it unnecessary to buy the spanner wrench put some masking tape on the blade of the screw driver to prevent marring.