A lid borrowed from another saucepan appears to fit until steam makes it rattle or the handle becomes awkward to reach. Similar diameter is only one part of compatibility. The rim, shape, material and intended use also matter.
Check the match while everything is cool
Start with the cookware maker’s replacement-part information. A model number or product range can be more useful than a rough measurement across the top. Some lids rest inside a rim; others sit over it. Two items described with the same nominal size may meet the pan differently.
With the pan and lid cool and empty, check that the lid sits securely without being forced. Look for wobbling, a trapped handle or an edge that could slip into the pan. Do not use a cracked glass lid, loose handle or damaged rim.
Consider how you will lift it
Imagine the pan in its normal cooking position. Can you grip the handle with suitable protection without reaching across another burner? Is there a safe, heat-resistant place to set the lid down? A lid that fits the pan but is difficult to handle is not a useful improvement.
Follow the manufacturer’s temperature and care instructions. Oven suitability, dishwasher suitability and stovetop use are separate questions. A metal-looking handle does not establish an oven temperature rating.
Keep ordinary lids separate from pressure equipment
Pressure cookers and similar appliances require their specified lids, seals and safety components. Do not adapt an ordinary saucepan lid, obstruct a vent or improvise a tighter seal. This check concerns ordinary compatible cookware, not modifications to pressure systems.
If the correct replacement is unavailable, choose a cooking method or piece of cookware that works without improvisation. For a household with many pans, label the storage positions or keep matched sets together. Finding the right lid before heating the pan is easier than solving the mismatch while food is already cooking.