One contract in a multi-leg strategy. On its own it may not be directional. Sometimes called “leg” or “side”. Finviro's term: “Option Leg”.
What is a “leg”
An Option Leg (Option Leg) is a single contract inside a larger structure: a spread has two legs, a condor four, a collar a stock position and two options. Each leg has its own direction, strike and expiration. The full meaning lives in no single leg but in the relationship between them.
Why the concept matters to a flow reader
Flow screens sometimes show legs separately. Selling ten thousand calls looks glaringly bearish, until you find ten thousand bought at a lower strike in the same instant, and the trade is a bull call spread. Reading a lone leg is the most common source of flow misreadings.
Execution as a package
Structures usually go out as a single combined order at a net price, so the legs fill together or not at all. That protects against a “stranded leg”: one leg fills, the market moves before the second, and the structure is distorted from birth.
Hypothetical example
A flow screen shows, in the same second: a purchase of 5,000 puts at the $100 strike and a sale of 5,000 at the $90 strike. This is not double panic. It is a hedging spread with a calculated cost: two legs of one idea.
Common mistake
Copying one leg of someone else's structure: someone sees a put purchase, buys the same, and it was actually a collar on a large stock position. They copied the hedge without the thing it hedged, and ended up with a naked bet nobody intended.
Why you manage the structure, not the single leg
Each leg has its own price, spread and delta, but risk belongs to the structure as a whole. Closing one leg of a four-leg spread removes the protection and turns a limited-loss position into an uncovered one. That is why a structure is opened and closed as a single order whenever possible, and split only by someone who knows what stays exposed.
Where to see it on the platform
The options calculator builds structures leg by leg and shows the net result, and the flow tools place simultaneous legs side by side so you read a structure, not fragments.
The structures calculator shows each leg alone and the combined result together, so you can see the effect of closing any one leg.
