With the project being developed along the book, we are going to apply some of these advanced layer commands:
LOCKLAYERcommand and select one of the visible parts edges. The OUTLINE layer has been locked. If we try to erase or modify entities in this layer, we get the information that these belong to a locked layer.
ACTIVATELAYERcommand and select the SECTION AA text. The CUTTING TEXT layer becomes current.
FREEZELAYERcommand and select one of the dimensions and the table. As we select entities, their layers are being frozen. So, DIMENSION and TABLE layers are frozen.