The Wollensak shutter has a lever to temporarily open the lens for composing. I never use it. I set the shutter to T and then cock and fire the shutter. Then I compose, and fire (don't cock) the shutter again to close it.
B is for "Bulb" -- cock, pressing the release opens the blades, while the release is held.
T is for "Time" -- cock, press the release to open the blades, press the release again to close the blades.