A doubles team consists of two players. Teams deliver five stones per end, after one stone from each team is pre-placed in either a guard or counter position. A team who loses an end gets "The Decision", rather than "The Hammer"; meaning they get to decide who gets the pre-placed counter, which in turn determines who gets The Hammer.

1. Each team shall deliver five stones per end. The player delivering his/her team's first stone of the end must also deliver his/her team's last stone of that end. The other team member shall deliver the team's second, third and fourth stones for that end. The player delivering the first stone can change from end to end. 
2. No stone, including those in the house, can be removed from play prior to the delivery of the fourth thrown stone of an end. If there is a violation, the delivered stone shall be removed from play, and any displaced stone(s) shall be replaced to their original position by the non-offending team. 
3. Prior to the start of every end, one stone of each team shall be placed as "stationary" stones. The team with the "Decision" shall decide to place their team's stationary stone, and their opponent's stationary stone, in either position A or B.
• (Position A). A stone bisecting the center line, midway between the hog line and the front of the house; or 
• (Position B). A stone on the back half of the button, bisecting the center line and touching the tee line. 
4. The team having the decision on the placement of the stationary stones shall be: 
• Unless predetermined, the teams opposing each other in the game shall use a coin toss to determine which team has the decision in the first end. 
• Following the first end, the team that lost the end will have the decision on the placement. 
• If an end is blanked, the team that did not deliver the last stone in that end shall have the decision on placement in the next end. 
5. The team whose stationary stone is placed in the position in front of the house shall deliver first in that end, and the team whose stationary stone is placed in the house shall deliver the second stone of that end. 
6. Scoring is the same as in regular curling. 
7. Each game will consist of eight ends. If at the completion of the scheduled ends the score is tied, play shall continue for the extra ends required to determine the winning team. 

In other words: 

The stationary rocks are a perfect high guard and a perfectly hidden counter.

By deciding whose stationary stone is the hidden counter, you've also determined the hammer. By placing your stone in the house, you've taken hammer.

Instead of explicitly getting "the Hammer" in an end, you get "The Decision" as to whether you get the hammer and stationary counter.  If you win the coin toss, or lose an end, then you get "The Decision".  If you have "The Decision,” then your team gets to decide where to place the two stationary stones, as specified in #3 above. 

The first three rocks thrown can not be takeouts, even for stones in the house. Counting the two stationary stones, there will be five rocks in play before you can throw a takeout. Therefore, one would expect this format to evoke a lot of touch shots and that there would be a lot of rocks in play at hammer time.

Contrary to regular curling, a blank end does not automatically result in retention of the "Hammer.”  After a blank end, the team that did NOT have "hammer" in the blanked end, gets the "decision" for the next end.  One would therefore expect the hammer to switch sides in most cases.