Cloud the bottom of the hierarchy. Clouds in the troposphere assume five physical forms based on structure and process of formation. These forms are commonly used for the purpose of satellite analysis. They are given below in approximate ascending order of instability or convective activity. "Non-convective" stratiform clouds appear in "stable" airmass conditions and, in general, have flat sheet-like structures that can form at any altitude in the troposphere. The stratiform group is divided by altitude range into the genera cirrostratus (high-level), altostratus (mid-level), stratus (low-level), and nimbostratus (multi-level). Fog is commonly considered a surface-based cloud layer. The fog may form
Self-adhesive plastic sheet Self-adhesive plastic sheet Self-adhesive plastic sheet, known in the United Kingdom as sticky-backed plastic, is wide plastic sheet or film with an adhesive layer on one side, used as a surface coating for decorative purposes. It is typically smooth and shiny, but can also come in textured varieties, in which case it can sometimes be used as a cheap alternative to veneer. The plastic is often PVC. The sheeting is typically sold with a removable paper release liner to prevent it from adhering prematurely. Self-adhesive vinyl sheet was introduced to the UK market in the 1960s under the brand name