I have a similar setup on my boom and it is certainly a component of your main sail reefing system. If you have two reefing points on the mail I would suggest you should have two blocks on the runner.
The reefing line should pass through a hole on the block, go under the boom, up through the clew on the main sail, back down to the block, along the boom to another pully mounted on the forwarded end of the boom, down to the base of the mast and through a pulley, forward to the cabin and cleat(take a breath).
With respect to the outhaul there should be a pully mounted in the end of the boom. The outhaul passes around the pulley and inside the boom. Inside the boom there should be another block which will creat purchase on the outhaul line 2:1 ratio. One end of the rope going through this pulley should be secured by a bolt going transverse through the boom, the other end goes through the block, forward towards the mast, out of the boom around another pulley, back towards the stern of the boat on the outside of the boom where it can be tensioned and cleated off with a cleat on the outside of the boom.
Hard to explain in writing but I hope this is of some assistance.