A shelf holds two stacks of items. Items stored in it will not deteriorate due to exposure.
A shelf's default storage settings are weapons only. Click the
Storage tab above the inspect pane to configure the shelf to store other types or items.
The command icons (Copy settings, Paste settings) can be used to copy storage settings between shelves. Settings can also be copied to other containers like stockpile zones and dumping stockpile zones. The copy function can take settings from one container and apply them to many containers, when shift-click is used to select multiple.
In Alpha 16, it was known as the Equipment rack and can only store mortar shells, weapons or apparel.