A 0DTE option expires today. If you buy it in the wrong place, there is no tomorrow for it to come back. So the check that matters most happens before the order, and it is about location. Where is price on the dealer map right now? The check is the same whichever broker holds your account.
Question one: which side of the flip
The gamma flip is the price where dealer positioning changes sign. Above it, dealers are generally long gamma, and their hedging leans against moves. Below it, they are generally short gamma, and their hedging adds to moves. The gamma flip covers the mechanics.
For a same-day buyer this changes what kind of day to expect. Above the flip, moves tend to be smaller and to fade. A long option needs movement, so a quiet regime works against it. Below the flip, moves can extend, in either direction. Neither side is good or bad. They are different conditions, and the same order behaves differently in each.
Question two: how far to the nearest wall
The call wall and the put wall are the strikes holding the most call and put gamma. Price often slows near them because hedging flow concentrates there. They are not fixed barriers, a point made at length in walls are not support and resistance.
Measure the distance from the current price to the wall in the direction of your trade. If you are buying a call and the call wall is a short distance above, most of the room you are paying for may already be used. If the wall is far away, the path is open, at least on the map.
Question three: what sits between you and the strike
Look at your strike against both levels. A call strike above the call wall needs price to go through the wall to pay. A put strike below the put wall needs the same on the downside. That can happen. It is a harder ask than a strike inside the walls, and the option’s low price reflects that.
Also check whether the flip sits between price and your strike. A move that has to cross the flip changes regime on the way. The flip is a boundary, not a target explains why that matters.
What the check does not do
It does not pick a direction. It does not say the trade works. Dealer levels describe positioning at the time they were measured, and positioning shifts through the day as contracts trade. A level that held at ten can move by two.
The check does one thing. It replaces “I think it goes up” with a sentence that includes the terrain: above the flip, a set distance under the call wall, strike inside the walls. If you cannot finish that sentence, you have not looked yet.
Where to read it
The Trader dashboard draws the flip, both walls, net GEX and the expected move on SPY, QQQ and IWM. Trader Pro refreshes on a 5-minute cycle and Trader Max is live. Read it, then go to your broker and decide. NoVo does not place the order and has no link to the account. If you trade in the Robinhood app, trading 0DTE on Robinhood covers the broker side.