LEVEL 1 Chapters 1­10 FIGuRE 3.5 Select Color, Color Books. 72 Layer Freeze/Thaw and On/Off Here we come to a very important part of the Layers dialog box. Freeze and Thaw are opposites of the same command, one that will make a layer disappear from view. The command freezes or thaws the layer for the entire drawing. Pick a layer, highlight it, follow the band across to the Freeze column and underneath you will find a yellow "sun" icon. If you click on it, that layer "freezes" and the icon becomes a blue "snowflake." Clicking again undoes the action. So what does freeze mean? It makes the layer (or rather all the objects on that layer) disappear from view, but remember, they are not deleted, only invisible. You will use this feature routinely in drawings to control what is displayed. The On/Off feature represented by the light bulb (yellow to blue and back) is essentially the same as Freeze/Thaw, with some subtle (and minor) details, so we do not go into them. You can use either method, though stay with Freeze/Thaw just to keep things consistent. Layer Lock/unlock This layer command, represented by the padlock, does exactly that; it locks the layer so you cannot edit or erase it. The layer remains visible but untouchable. The unlocked layer's icon is blue and looks "unlocked," while a locked layer's padlock turns yellow and changes to a "locked" position. Play around with all the buttons we mentioned thus far to get a feel for them. When done, make sure everything is reset (not locked or frozen) and click on the X in the upper corner of the Layer box to close it. 3.2 INTROduCTION TO LINETyPES Linetypes are the different lines that come with AutoCAD. As a designer, architect, or engineer, you may need a variety of lines to convey different ideas in your design. Just like in hand-drafting, where you created Dashed, Hidden, Phantom, and other line types to show cabinets, demolition work, or hidden geometry in part design, in AutoCAD you load the lines and use them as necessary.