Like most CAD systems, AutoCAD has layers to control the properties and visibility of objects. Objects on locked layers are visible, but cannot be edited.
AutoCAD 2006 now displays a padlock icon when you attempt to edit objects on locked layers, as illustrated below.
When you press Enter at the ‘Select objects or (select all):’ prompt, AutoCAD selects all objects (not on frozen layers), and then skips repeating the ‘Select objects:’ prompt -- going straight to the next prompt, 'Select object to trim or shift-select to extend or [Fence/Crossing/Project/Edge/eRase/Undo]:'.
Autodesk notes that the Crossing option (new to AutoCAD 2006) can be ambiguous. For that reason, AutoCAD follows the rectangular crossing window clockwise from the first pick point,selecting objects to trim. If, however, the first point you pick (for the Crossing option) is an object, AutoCAD abandons Crossing mode, and selects the one object. Clear as mud?
In AutoCAD 2005 and 2006, this command makes multiple copies by default. Press Enter to exit the command (and keep it from repeating):
Specify second point or [Exit/Undo]
The new Displacement option, however, makes this command act like it did in the old days (making one copy and then exiting); in addition, it displays the displacement from the prior use of the command:
Specify base point or [Displacement]
Specify displacement <1.0000, 2.0000, 0.0000>: (Press Enter, or enter a new displacement.)
Whether you press Enter or enter coordinates, AutoCAD displaces the selected objects, and then exits the command.
Fillet and Chamfer
You may already know that holding down the Shift key during either of these two commands causes AutoCAD 2006 to create zero-distance fillets and chamfers. AutoCAD's reminder is, however, worded differently: "Shift-select to apply corner."
(Can you tell I'm on the editing-objects chapter?)