-Use the full path name when matching names in the archive. @sc{gnu}
-@command{ar} can not create an archive with a full path name (such archives
-are not POSIX compliant), but other archive creators can. This option
-will cause @sc{gnu} @command{ar} to match file names using a complete path
-name, which can be convenient when extracting a single file from an
-archive created by another tool.
+Use the full path name when matching or storing names in the archive.
+Archives created with full path names are not POSIX compliant, and
+thus may not work with tools other than up to date @sc{gnu} tools.
+Modifying such archives with @sc{gnu} @command{ar} without using
+@option{P} will remove the full path names unless the archive is a
+thin archive. Note that @option{P} may be useful when adding files to
+a thin archive since @option{r} without @option{P} ignores the path
+when choosing which element to replace. Thus
+@smallexample
+ar rcST archive.a subdir/file1 subdir/file2 file1
+@end smallexample
+will result in the first @code{subdir/file1} being replaced with
+@code{file1} from the current directory. Adding @option{P} will
+prevent this replacement.