Contract Asuran Outsourcing
I think when you want to be building a large guild upgrade but don’t want to put all your banners on hold? Or maybe when you want to build more than one banner at once.
Basically, once you’ve got enough influence coming in that you can be building things frequently.
The “Contract Asuran Outsourcing” consumable is a one-time use deal that lets you put one upgrade onto an extra build track. As Gil said, they’re more useful for a large/active guild that has a lot of influence coming in.
I use them on those expensive upgrades that take a while (any level 3, 4, or 5 unlocks or the Guild Treasure Trove or Deep Cave, for example). That way the construction of that upgrade doesn’t take up a normal build slot for three days or a week that I’d normally use for banners, MF bonus, or Gather bonus.
You use the Contract Asuran Outsourcing by first queuing up the item you want on this “side track” to be next on the build order. So if you are currently working on two banners and want to use the Contract on Arch 3, add Arch 3 to the queue (so that it would be next in line to start) and then use the Contract to start it. Anything in the queue after Arch 3 will then start after your banners are finished – Arch 3 is never bumped onto your normal build tracks.
Note that you can only have one thing in the Contract Asuran Outsourcing slot at a time, and you can only save one Contract Asuran Outsourcing at a time, so no stocking up and building all those WvW fort buffs at the same time!
Hope this helps! If you have any specific questions (or if I completely confused you) please let me know.