A manual page a day... Click here to see the manual table of contents.
Locking a layer makes it easy to refer to information contained on the layer, but prevents you from accidentally modifying its entities. When a layer is locked (but visible and thawed), its entities remain visible, but you cannot edit them. If you lock the current layer, you can still add new entities to it. You can also change the linetype and color associated with a locked layer. Unlocking a layer restores full editing capabilities. For details See Locking and unlocking layers.