A molded plastic sliding panel used for covering an exterior building wall surface is made up of a body portion, an attachment portion provided above and adjacent to the body portion, a top locking portion extending horizontally across an upper portion of the sliding panel and a bottom locking portion provided at the bottom of the body portion. The top locking portion is adapted to engage with the bottom locking portion on an upper adjacent siding panel. The attachment portion can contain a plurality of apertures provided therein which sequentially become more elongated as they are positioned toward a side edge of the attachment portion in order to deal with thermal expansion and contraction of the panel.