If you are still having trouble finding a term that adequately
matches your invention in the Index to the U.S. Classification System or can't
find the right code in the Manual of Classification, you can do a keyword search.
However, only patents since 1976 can be searched by keyword.
On that page, click on the link titled Search for Patents.
Finally, under Searching Full Text Patents (Since 1976), click on the link titled Advanced Search.
In the Query box, type in your search terms. For our invention we enter
"computer mouse" in the query box (be sure to include quotation
marks around the search terms in this instance). This will return a list
all the patents that have "computer mouse" anywhere in the indexed
text. (For more information on how to perform an advanced search, click
"Help" button at the top of the page. Then click on the "How
to Use the Advanced Search Page" link).
Click on a patent number. You may notice that some patent
numbers have a "D" before the number. This indicates that the patent
is one of design instead of utility. Focus on the Abstracts, Current
class and subclass numbers, and the claims. In fact, this is often a good
time to go back to the Manual of Classification to see the context or a
class/subclass. And finally, don't forget to look at the drawings. These
are often a surefire way to determine your invention's uniqueness.