You can backtrack your recent actions using one of several methods
The simplest method of backtracking is to use the UNDO or Ctrl+Z commands to undo a single action.
You can reverse the effect of UNDO command by using REDO (Ctrl+Y) immediately after using UNDO.
You can erase selected objects from the drawing. • Click Menu “Editor/Erase”• Select objects to remove
You can cancel a command without completing it by pressing Esc.
• Right click choose “repeat”• Press spacebar
You can clean up your drawing by removing unused items in your drawing such as unreferenced layers, blocks, and style definitions.
• Click menu “Tools/Purge”• Check the objects to purge• Check if you need verify each name to be purged, enter Y or N.
Use BREAK to create a gap in an object, resulting in two objects with a gap between them.
Use JOIN to combine lines, arcs, elliptical arcs, polylines, 3D polylines, splines, and helixes by their endpoints into a single object.
Changes the length of objects
You can specify changes as a percentage, an increment, or as a final length. LENGTHEN is an alternative to using TRIM or EXTEND.
Changes the length of an object by a specified increment, measured from the endpoint that is closest to the selection point.
Sets the length of an object by a specified percentage of its total length.
Sets the length of a selected object by specifying the total absolute length from the fixed endpoint. Total also sets the included angle of a selected arc by a specified total angle.
Join the corner of two lines