By creating layers, you can associate similar types of objects by assigning them to the same layer. For example, you can put construction lines, text, dimensions, and title blocks on separate layers. You can then control
As you draw, AutoCAD places newly created objects on the current layer. The current layer may be the default layer (0) or a layer you create and name yourself. You switch from one layer to another by making a different layer current, and any subsequent objects you create are associated with the new current layer and use its color and linetype. You cannot make a layer current if it is frozen or if it is an xref-dependent layer.
You can make drawing layers invisible either by turning them off or by freezing them. Turning off or freezing layers is useful if you need an unobstructed view when working in detail on a particular layer or set of layers or if you don't want to plot details such as reference lines. Whether you choose to freeze layers or turn them off depends on how you work and on the size of your drawing.
Turn a layer off rather than freezing the layer if you frequently need to switch a layer's visibility. When you turn a layer back on, the objects on the layer are redisplayed automatically.
Freeze a layer if you do not need to see the objects on that layer for a long period of time. You redisplay frozen layers by thawing them, and thawing one or more layers causes the drawing to be regenerated. Freezing and thawing layers takes more time than turning layers on and off.
Objects on turned-off layers are invisible, but they still hide objects when you use HIDE. Objects on frozen layers do not hide other objects.
In paper space, you can make some layers invisible only in certain viewports. You can also freeze the current layer in one or more floating viewports. For more information about paper space, see Creating the Drawing Layout.
Each layer has an associated color and linetype that can be applied to all objects on that layer. If the Color control on the Object Properties toolbar is set to BYLAYER, the color of new objects is determined by the color setting for the layer in the Layer & Linetype Properties dialog box. If you set a specific color in the Color control, that color is used for all new objects, overriding the default color for the current layer.
The same is true for linetypes and the Linetype control on the Object Properties toolbar.
The BYBLOCK setting should be used only for creating blocks. For more information, see Controlling Color and Linetype Properties in Blocks.
When a layer is locked, none of the objects on that layer can be modified until you unlock the layer. Locking layers reduces the possibility of modifying objects accidentally. You can still apply object snaps to objects on a locked layer and perform other operations that do not modify those objects.