When ‘shàngbiān’ expresses the spatial relationship of coincidence, it requires direct or derived contact of the located object and the reference object. The reference object may be a surface or a line. Its specific meaning is determined by the semantic and pragmatic context, as shown:
Zhuōzi shàngbian fàngzhe yī ge qiú.
(On the table was placed a ball.)
Shéngzi shàngbian liàng zhe liǎng jiàn yīfu.
(On the clothes line were airing two pieces of clothing.)
1c. 山顶上(边) 有一个塔。
Shāndǐng shàng yǒu yī ge tǎ.
(On top of the hill there is a pagoda.)
Dīngzi shàng guàzhe yī dǐng màozi.
(On the nail was hanging a hat.)
In all the cases of (1), the located objects and the reference objects have the relationship of contact or ‘coincidence’. Chinese differentiates types of coincidence by relying on the semantic contents of the two spatially related objects. Thus in (1a), the ‘ball’ has contact with a two dimensional reference object, namely, the top of the table. In the case of (1b), the located object ‘the clothes’ have contact with a linear or one dimensional reference object ‘the clothesline’, while in the situations of (1c, d), the coincidence of the located and the reference object is the overlap of points, it has the punctual nature.
 Loar, J. K. (2011). Chinese syntactic grammar: functional and conceptual principles. New York: Peter Lang.