Optimistic about holding a good position (already holding goods), when the market drops and the margin is insufficient, the broker will inform the holder that it is necessary to increase the margin (or make up the position). This market situation can be called that the holder is trapped.
Bears hold short positions (sold). When the market price rises and the margin is insufficient, the brokerage firm will inform the holder that it is necessary to increase the margin (or cover the position). This market situation can be called that the holder is trapped.
For example, doing futures investment and arranging stock investment with stock financing. Will have a chance to get caught.
Usually, when the market is in a favorable atmosphere, the market suddenly turns sharply and falls, and people with good positions will be described as being trapped. Or the market suddenly turns to a sharp rise in profits and losses, and people who are short positions will also be described as being trapped.