Recently, a beginner asked me what the inside and outside plates in trading software mean. Honestly, understanding these two concepts can save you a lot of money. Many people actually get them reversed. Is the inside plate a buy or a sell? Today, I’ll clarify this.

Simply put, the inside plate is when sellers actively transact at the bid price, indicating that sellers are more eager. The outside plate is when buyers actively transact at the ask price, indicating that buyers are more eager. In other words, a high number of inside plate transactions suggest heavy selling pressure, while a high number of outside plate transactions suggest strong buying momentum. Many people mistake the inside plate for buy orders, but actually, it reflects sellers’ urgency.

Let me give you an example. Suppose someone places a buy order for 1,415 shares at $1,160, and someone else places a sell order for 281 shares at $1,165. If you want to sell immediately, you might sell 50 shares at $1,160 directly. These 50 shares are considered the inside plate because you, as the seller, actively matched the buyer’s price. Conversely, if someone wants to buy immediately and places a buy order for 30 shares at $1,165, these 30 shares are the outside plate because the buyer actively chased the seller’s price.

Once you understand whether the inside plate is buy or sell, it becomes much easier to analyze the inside-outside ratio. The ratio is calculated by dividing the inside plate volume by the outside plate volume. A ratio greater than 1 indicates more inside plate transactions, suggesting more bearish sentiment, with sellers pushing prices down. A ratio less than 1 indicates more outside plate transactions, suggesting bullish sentiment, with buyers chasing prices; this is usually a buy signal. A ratio equal to 1 indicates a balance between buyers and sellers, meaning the market is in stalemate.

But there’s a trap to watch out for. Many people see the outside plate volume larger than the inside plate and think the price will go up, but they get fooled by the big players. Major traders often place a bunch of buy orders to lure retail investors into buying, while secretly selling off shares—this is called “inducing buying.” The opposite can happen too, where they place sell orders to trick you into selling, while they’re actually accumulating shares—this is “inducing selling.” So, understanding whether it’s buy or sell isn’t enough; you also need to consider price trends, volume, and order book structure to avoid traps.

A more useful approach is to focus on support and resistance zones. When the price drops to a level and can’t go lower, that’s a support zone. At this point, even if the inside plate volume is high, don’t worry too much because there are buyers stepping in. Conversely, if the buying pressure can’t push through a certain price level, that’s a resistance zone. When that happens, it’s time to consider taking profits. Trading between support and resistance—buying at support and selling at resistance—is more reliable than just looking at the inside-outside ratio.

Honestly, inside and outside plates do have advantages: data is real-time, concepts are simple, and they can quickly reflect the market sentiment of buyers and sellers. But they also have obvious drawbacks—they can be manipulated by big players, are short-term in nature, and can be distorted if used alone. Therefore, it’s best to combine them with volume, technical analysis, and fundamental factors.

In summary, the inside plate indicates seller urgency, and the outside plate indicates buyer urgency. The answer to whether it’s buy or sell is that the inside plate fundamentally reflects seller behavior. But in actual investing, don’t rely solely on this indicator; combine it with other factors like fundamentals and overall market trend. Relying only on the inside-outside ratio won’t be enough to navigate the stock market effectively.