The Guildworkers' Union manages the trading of manufactured crafts and the exchange of Guild Points. In other words, once you are a member, you can synthesize certain requested items and trade them for guild points.
You must be a skill level 28 (or higher) and attain the rank of Novice before you can join a union. You can only be a member of one (1) union at a time. If you are member of one union and wish to join a different union, you must terminate the existing contract. As of the March 2011 Update, Guild Points are no longer lost when transferring guilds, but they remain unavailable for use until you switch back to the guild for which they were earned. Be aware, you will not be able to gain any guild points the first earth day you switch; gated by Japanese midnight.
Accumulating Guild Points
Everyday, by speaking to your Guildworker's Union Representative, you will be requested to provide a certain item. The item requested depends on your current skill rank. You will have a certain amount of time to provide as many of these items as you can synthesize or buy. You can check the available amount of time by asking the Representative about your current limitations.
The requested item changes each Earth day at Midnight in Japan. Additionally, the amount of guild points you can accumulate each day is limited - anywhere between 1,000 and 8,000. For example, on a given day, you might be limited to accumulating 1,000 points. Assuming the item you've been requested to provide is worth 100 points, you would only want to trade 10 items. Trading items after you have reached the limit will result in no points gained.
Note: It is possible to obtain the maximum number of guild points for an item on a given day, then achieve a guild rank-up and receive more points on the same day, with a new item. However, the new item must have a maximum guild point cap that is more than the old item, and the guild points you have already received are logged so that you can only receive a maximum accumulated total for the day, that does not exceed the total of the new item.
Example: The craftsman guild point item for the day caps at 2000 guild points which you obtain. You then rank up to Artisan rank on the same day, whose guild point item caps at 5000 guild points. You have already obtained 2000 points for the day, but may now trade in some of the new item to obtain another 3000 guild points, for a total of 5000 guild points for the day.
When the time limit has expired, the item requested by the guild will change. It will also change in the event your craft rank rises.
Given a particular crafting rank (Novice through Veteran), each day the item requested will come from the next higher rank until you reach the current rank. For example, a Novice crafter's requested items will rotate between Amateur, Recruit, Initiate, Novice, and then back to Amateur. A Veteran crafter will rotate between all ten crafting ranks. This means there is a rotation of 2,520 days (the lowest common denominator of 4,5,6,7,8,9, and 10) or almost seven years. The last time when all crafting ranks had the same requested item rank was from nov 25th 2008 through nov 28th 2008.
The current day's requested item is the same rank throughout all crafts. If an Alchemy Artisan is asked for an Apprentice level item, a Woodworking Artisan will also be asked for an Apprentice level item.
There are (at most) eight possible items per guild per crafting rank. (Some guilds have fewer than eight items for some ranks.) Several sites track these possible items and group them into patterns commonly called A through H. The order of the patterns appears to be random. However, once you have correctly identified the pattern for any single rank in any single guild, you know the item for all guilds and ranks for that day.
Using Guild Points
Each Guild has a Guildworker's Union Representative - this is the NPC that you turn items in to and purchase Guild Point items from. You can also speak to them for various information about your Guildworker contract.
Possible Guild Pattern Items