What is this valve/ nub?

[goaliemandan13]

Had some engine and transmission work done a couple weeks back. While looking under this weekend, noticed this valve. The picture is on the driver side, looking towards the front of the truck. Small silver nut/valve above the main line. Should something be attached to it? I'm a novice when it comes to transmissions.
2003 2.3 L 5-Speed
M5OD-R1

Thanks

 

[2 bronco 11s]

that's the bleeder for your clutch. some have a rubber cap over them

 

[Elutheros]

To be just a little more precise, it's the bleeder screw for the clutch slave cylinder in the bell housing of the transmission. The process for bleeding the clutch master cylinder mounted on the firewall forward of the clutch pedal is tedious and time consuming. Bleeding the slave cylinder is a lot simpler.

 

[dvdswan]

Welcome to the site.