If you are a GM at any guild event, you have a responsibility to make sure your players are comfortable and know about these safety tools. As a player, you need to be familiar with the below safety tools.

The X-Card
The X-Card is traditionally a piece of card with an X on it. It allows players and GMs to stop play and address a part of the game they’re uncomfortable with.
At any point in the game any player or GM may tap the card to indicate they are uncomfortable with what is happening and to skip it. Alternative gestures and signifiers can also be used, as long as it's clearly communicated. A common substitute is someone making an X gesture with their arms across their body.
The person who used the card should indicate what content made them uncomfortable. They do not have to explain why it made them uncomfortable. From there, the content can be changed, faded to black, or a short break can be taken if needed, as appropriate. Under no circumstances should the X-Card be ignored when used.
The X-Card can also be used to make sure the tone of the game stays on track. We encourage player creativity, but if a player does something wildly out of genre in a serious game, the X-Card can be used.

For more information, view The X-Card by John Stavropoulos.

The Open Table Policy
The open table policy allows anyone to step out of the game for any reason.
Sometimes there is an urgent phone call, or some other emergency, or a player just isn’t feeling a session. We are often playing with strangers and often emergencies are highly personal, the open table policy allows players to leave the table without needing to provide a detailed explanation. A simple “I’m sorry I have to go” is all that’s required. 
Players who leave via this policy are welcome to return if they wish. If a player decides that they do not want to keep playing for any reason they may make it clear that they are leaving the game and do so without explanation.

Lines and Veils
Lines and veils are terms used to convey the limits of the game.
They might include subject matter that participants find objectionable or traumatic and do not wish to interact with. Lines are themes or elements that a participant wishes to be off-limits entirely. When you establish a line that content does not come up in the game no matter what. Veils are themes or elements that a participant does not wish to interact with directly but can be alluded to. Typically, veiled material is only implied or very briefly mentioned and immediately cut away from by the GM.

For one shots without a session 0 like at Convergence, there may not be time to go through a full lines and veils process. This is why it’s important to make the expected content of your game clear in your game description, and make sure players know about the other safety tools.