Definition: Used as a function word to indicate position in contact with and supported by the top surface of.
This sign is a standalone for the English word "on" for its sake but in practice, it's rarely used in ASL. When using it, one often fingerspells it. E.g. LIGHT+#ON.
Most ASL prepositions are incorporated into verb phrases and classifier phrases.
This fingerspelled loan is also commonly used in some contexts.
Gloss: paper[t] cl-paper pen[t] cl-pen[loc]
English equivalent: a pen on the paper
Use a passive (e.g. left-handed) classifier for the paper and a dominant classifier (e.g. right-handed) for the pen if you're right-handed signing.