While useful for reducing a large quantity of situational factors into a more manageable profile, the SWOT framework has a tendency to oversimplify the situation by classifying the firm's environmental factors into categories in which they may not always fit. The classification of some factors as strengths or weaknesses, or as opportunities or threats is somewhat arbitrary. For example, a particular company culture can be either a strength or a weakness. A technological change can be a either a threat or an opportunity. Perhaps what is more important than the superficial classification of these factors is the firm's awareness of them and its development of a strategic plan to use them to its advantage.
This example also illustrates how threats can become opportunities (and vice versa). The limitation of tin cans (which aren't biodegradable) creates an opportunity for leadership in developing biodegradable containers. There are several formats you can use to do a SWOT analysis, including a basic SWOT form that you can use to prompt analysis, but whatever format you use, don't be surprised if your strengths and weaknesses don't precisely match up to your opportunities and threats. You might need to refine, or you might need to simply look at the facts longer, or from a different angle. Your chart, list or table will certainly reveal patterns.