Most of the time, price moves in a continuous stream — you can watch it tick from one level to the next, and an exit placed anywhere along the way will be reached as price passes through. But sometimes price does not pass through. It jumps, leaping from one level to a distant one with no trading in between. This is a gap, and it is the one situation where the safety net most traders rely on — the stop — can simply fail to catch them at the price they expected.

This article explains what a gap is, why it happens, why it makes "I'll just set a stop" an incomplete plan, and what overnight risk really means. By the end you will understand that a stop defines your intention, not a guarantee — and you will size with that distinction in mind.

What a Gap Is

A gap is a discontinuity in price: the market reopens or re-prices at a level meaningfully away from where it last traded, with no transactions occurring in the space between. On a chart it looks like a visible jump — an empty vertical space where price teleported rather than traveled. The defining feature is that nobody traded in that gap. There were no prices to fill an order at, because the market skipped over them entirely.

Gaps happen most often across breaks in trading — overnight, over a weekend, or around a scheduled event — when significant new information arrives while the market is closed or thin. All the reaction to that information compresses into the moment trading resumes, and price simply reopens wherever the new balance of buyers and sellers sets it. The adjustment that would normally play out across many small moves happens in a single leap.

Why Gaps Break the Stop You Trusted

A stop is an instruction: "if price reaches this level, get me out." That instruction works smoothly when price travels through your level, because there are trades happening at and around it. But a stop does not guarantee the price — it guarantees an attempt to exit once your level is reached or passed. If price gaps straight past your stop, your exit happens at the next available price on the other side of the gap, which can be far worse than the level you set.

This is the crucial, often-painful lesson: a stop placed at a 1R loss does not guarantee a 1R loss. It guarantees you will be taken out when the market trades through that level — but if a gap leaps over it, the realized loss can be several times what you planned. The stop defined your intention to risk 1R. The gap decided the actual number. Treating a stop as an ironclad cap on losses is a misunderstanding of what it can promise.

The Mental Model: The Missing Stair

Imagine walking down a staircase in the dark, expecting each step to be where the last one was. Normally this works — the steps are evenly spaced and you descend smoothly. But suppose one stair is missing, and instead of a single step down there is a sudden drop to the floor below. Your foot reaches for the expected step and finds nothing until much further down. A gap is that missing stair. Your stop assumed price would arrive step by step, giving it a place to act. When the stair is missing, price drops past where you reached for it, and you land much harder than you planned.

You cannot make the staircase continuous — gaps are a feature of how markets digest information while closed or thin. What you can do is account for the missing stair in advance: assume that any position carried across a break in trading might land harder than its stop suggests, and size it so that even a bad landing is survivable.

What Overnight Risk Really Means

"Overnight risk" is the exposure you carry when you hold a position through a period when you cannot react — when the market is closed or when you are not watching. During that window, information can arrive and price can re-price against you with no opportunity to manage the position as it moves. The entire adjustment lands at once, as a gap, when trading resumes. This is why holding through a closed market is categorically different from holding during active hours: in active hours you can respond to a move; across the gap, you cannot.

The implication is not "never hold overnight" — many sound approaches do, deliberately. The implication is that a position carried across a break carries a different, larger kind of risk than the same position during active trading, and it deserves to be sized with that in mind. The protection is not a tighter stop, which a gap can leap over anyway. The protection is a smaller position, so that even an adverse gap costs an amount you chose to accept.

Managing Gap and Overnight Risk

Treat the stop as intention, not guarantee. Assume your realized loss could exceed your planned loss when a gap is possible, and never size as if the stop were a hard floor.
Size down for carried risk. A position held across a closed or thin market should generally be smaller, because the worst case is wider than a continuous-market stop implies.
Know when gaps are likeliest. Breaks in trading and scheduled events are when information piles up against a closed market. Carrying maximum exposure into those windows is carrying maximum gap risk.
Decide carry deliberately. Whether to hold across a break should be a conscious decision about accepting a different risk profile — not a default you drift into because you forgot to close.

Common Mistakes

Believing a stop caps the loss. A stop is an exit instruction, not a price guarantee; a gap can fill it far beyond the intended level.
Sizing overnight positions like daytime ones. Carried positions face a wider worst case and warrant smaller size, not the same size with a tighter stop.
Carrying maximum exposure into scheduled events. The windows where gaps are likeliest are exactly when reducing exposure matters most.
Drifting into overnight holds. Holding across a break by inattention rather than by choice means accepting a risk you never actually decided to take.

Simulator Exercise

In Abu Terminal, work through events where price moves sharply between one period and the next rather than smoothly within a session. For each, ask: if I had held a position into that jump with a stop on the other side, where would I actually have exited — at my stop, or at the worse price on the far side of the gap? Estimate the difference between the loss you planned and the loss you would have taken. Doing this repeatedly builds the instinct that a stop is a plan, not a promise, and that carried positions deserve smaller size precisely because of the moves you cannot trade through.

Reflection Prompt

Write an answer to this: For the positions I would typically carry across a closed market, am I sizing them as if my stop guarantees my loss — or as if price could gap well past it? If a position gapped twice my planned loss against me overnight, would that be survivable or serious?

Quick Check

What is a gap, and why can no order be filled inside it?
Why does a stop fail to guarantee the exact loss you planned when a gap occurs?
Why is the right protection against overnight risk usually a smaller position rather than a tighter stop?

Answers: (1) A discontinuity where price re-prices to a distant level with no trading in between — there are no transactions at the skipped prices, so no order can fill there. (2) Because a stop only triggers an exit once its level is reached or passed; if price gaps over it, the fill happens at the next available price beyond the gap, which can be far worse. (3) Because a gap can leap over any stop level regardless of how tight it is, so only reducing size limits the worst-case loss to an amount you chose to accept.

Gaps and Overnight Risk: The Move You Cannot Trade Through