Some etches undercut the masking layer and form cavities with sloping sidewalls. Movable sections of steel forms were used for the sidewalls. The body is a monocoque structure with integral frames and sidewalls. K forms slanted obstructions diverging from the sidewalls, creating turbulence across the boreline. The thickness of the buttress sidewalls ranges from at the base to at the crest. This process produces trenches with highly vertical sidewalls. In this process, etch depths of hundreds of micrometres are achieved with almost vertical sidewalls. Tires with sidewalls made of natural rubber are called "gum wall". These savings are realized because less energy is wasted flexing fewer tire sidewalls. The eaves of the sidewalls feature stone-made filigree work. Some tires have a reflective strip on their sidewalls to improve visibility at night. Tires come with standardized tire code sizing information, found on the sidewalls of the tires. The sidewalls give the tire resistance against the environment. Often, in addition to sidewalls, Plexiglas panels are used as a safety measure. The CCEMG railgun included several features&colon; ceramic sidewalls, directional preloading, and liquid cooling.