barry grant air solenoid and relay combo

i was given a Barry grant solenoid and relay combo to use for air shifter solenoid. with no wires hooked up to relay air flows thru . With it being a 3 prong relay how should this be wired . there is one prong on relay that is larger than the other two. as Barry grant no longer has a web site is this the correct use for this relay or what was its purpose. Is this a three way valve as there is 3 ports for air and a screw on bottom of valve which can be turned . One inlet for air comes thru top of relay and two ports are on sides of solenoid . Relay is screwed into top of solenoid and must be used as a set.