Idea of Select All Icon
This image depicts a textual document that is relatively filled with writing. The entire square is bordered by a dotted line. It appears to contain the entirety of the document, as opposed to just the lines that are currently visible.
This Select All icon is made in Material Design style
developed by Google. This style is based on extremely simplified shapes, thin two-pixel lines, and is optimized for 24x24 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 6,100 icons, all in the same style and quality.