From FIXwiki

FIX Message Component SecurityTradingRules

FIX Specification	Type	First introduced	Deprecated
Common	Block	FIX.5.0

Ths SecurityTradingRules component block is used as part of security definition to specify the specific security's standard trading parameters such as trading session eligibility and other attributes of the security.

Component Contents By FIX Version

Notes

Please post comments, clarifications, examples here. Click on the edit button on the right and away you go! 

Don't forget to refer to the FPL Discussion Groups to back up anything you write.
You will often find the authoritative statements on matters of FIX specification interpretation there.
Links from FIXwiki pages to relevant discussions on the FPL site are very valuable.

For example if you were writing a clarification on how to specify the "quantity" of an order in FIX, you might add the
following relevant link, http://www.fixprotocol.org/discuss/read/f5014573, to back up your points.