The Trigger Method defined in the IBApi.Order class specifies how simulated stop, stop-limit, and trailling stops, and conditional orders are triggered. Valid values are:

0 - The default method for instrument
1 - "Double bid/ask" function, where stop orders are triggered based on two consecutive bid or ask prices.
2 - "Last" function, where stop orders are triggered based on the last price
3 - "Double last" function
4 - Bid/ask function
7 - Last or bid/ask function
8 - Mid-point function

Below is a table which indicates whether a given secType is compatible with bid/ask-driven or last-driven trigger methods (method 7 only used in iBot alerts)

secType	Bid/Ask-driven (1, 4, 8)	Last-driven (2, 3)	Default behavior	Notes
STK	yes	yes	Last	The double bid/ask is used for OTC stocks
CFD	yes	yes	Last
CFD - Index	yes	n/a	n/a	Ex IBUS500
OPT	yes	yes	US OPT: Double bid/ask, Other: Last
FOP	yes	yes	Last
WAR	yes	yes	Last
IOPT	yes	yes	Last
FUT	yes	yes	Last
COMBO	yes	yes	Last
CASH	yes	n/a	Bid/ask
CMDTY	yes	n/a	Last
IND	n/a	yes	n/a	For conditions only

Important notes :

If an incompatible triggerMethod and secType are used in your API order, the order may never trigger.
These trigger methods only apply to stop orders simulated by IB. If a stop-variant is handled natively, the trigger method specified is ignored. See our Stop Orders page for more information.