Roberts, Frank X. - Defining the Bookmark, BiblioBuffet Website (discontinued)
Perhaps lexicographers might be convinced (though it is doubtful) to limit “bookmark” or “bookmarker” to the definition of the collected item.
From the late 4th century A.D., when it seems the only bookmark available to St Augustine was his finger, to the present where they have become cultural artifacts as numerous as golf balls, bookmarks have remained extremely difficult to define.
Sonnet to a Bookmark
Patience, hard thing, but you my trusty mate
Have learned the way. Even left out in the rain,
Uncomplaining you mark the poet's old refrain,
"They also serve who only stand and wait."
Though drowned in coffee stains and many a tear,
Soldier-like you stand and keep the guard;
When weary heads begin to nod, you're there,
Between the pages keeping watch and ward.
There is a lesson in your quiet ways:
That we who frown and fret might try to learn
Like you awhile to stop and think and look;
To put some simple patience in our days,
And find at last the truth for which we yearn
Stands within, not on the pages of our book.