The first time you open an option chain it looks like a spreadsheet someone spilled. Hundreds of rows, a dozen columns, numbers in colours nobody explained, and somewhere in there is the one contract you meant to sell.

It is actually a simple object with a strict shape, and once you see the shape you can read any broker's version. Here is one you can click.

The shape is always the same

Every chain in every platform is built the same way: one expiration at a time, strikes running down the middle, calls on one side and puts on the other. Usually calls left and puts right, and usually the middle of the table is roughly where the stock is trading.

That layout is doing something useful. Reading across a single row gives you the call and the put at the same strike — which, as the moneyness lesson showed, are always in opposite states. Reading down a column shows how one quantity changes as you move away from the money.

What each column is for

Bid and ask. The bid is what someone will pay you right now; the ask is what someone will sell to you for. As a premium seller you are usually looking at the bid, because that is the price you can hit immediately. The gap between them is the spread, and it is a real cost.

Delta. The most useful single column for strike selection. It gives you a portable measure of how far out of the money a strike is, and a rough sense of assignment odds. “Sell the 20 delta” is a complete instruction; “sell the $92.50” is not.

Implied volatility. The volatility number that makes the model agree with the market price. Notice in the widget that it is not constant across strikes — downside strikes carry more. That is skew, covered in its own lesson.

Volume and open interest. Volume is contracts traded today; open interest is contracts currently outstanding. Both are liquidity signals, not direction signals — a strike with high open interest is easy to trade, not a prediction. Real chains show these; the widget above omits them because synthetic volume would be fiction.

Last. The price of the most recent trade, which may have been hours ago on a quiet strike. It is the least reliable column on the screen and the one beginners instinctively read first. Use the bid and ask.

Reading it as a seller, in order

A chain has hundreds of rows and you need one. This is the sequence that gets you there without wandering:

1. Pick the expiration first. Most platforms show one at a time for a reason. Thirty to forty-five days is the usual starting point — see theta for why.
2. Go to the put side. For cash-secured puts you are selling below the current price, so you want the rows beneath the money.
3. Find your delta. Scan the delta column for roughly 0.16 to 0.30, per strike selection.
4. Check the strike is one you would own at. Multiply by 100. If that number is uncomfortable, nothing else on the row matters.
5. Check the spread is tight. A wide bid-ask makes an otherwise good trade mediocre.
6. Read the bid, not the mid or the last. That is your realistic credit.

Identical strike, identical delta, identical obligation. The second row pays $145 instead of $185 because the market for it is thin — and it will cost you again when you close. The delta column alone would never have told you.

What can go wrong

Trading off the last price. Stale by definition.

Picking the wrong expiration. Chains for adjacent weeks look nearly identical. Check the date before you send the order, every time.

Confusing the call and put sides. Some platforms put calls on the right. Confirm which side you are on before selecting a strike.

Assuming high open interest means a good trade. It means a liquid one. Nothing more.