Day 15
Editing
70 XP

OFFSET + MIRROR

Duplicate parallel or reflected copies.

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Learning objective

By the end of this lesson you can create parallel copies at a fixed distance with OFFSET, and reflected copies across a line with MIRROR.

What OFFSET + MIRROR is

OFFSET creates a new object parallel to an existing one at a chosen distance. MIRROR creates a reflected duplicate across a chosen axis line.

Why and when you use it

Use OFFSET for wall thicknesses, contour lines, padding and inset shapes. Use MIRROR for symmetry — anything with a left/right or top/bottom mirror image.

Where to find it in the AutoCAD interface

Ribbon
Home tab → Modify panel → Offset / Mirror buttons.
Menu
Modify menu → Offset / Mirror.
Command line
Type OFFSET or MIRROR and press Enter.
Alias / shortcut
O for OFFSET, MI for MIRROR.

Key vocabulary

Offset distance
How far the new parallel object is from the source.
Side to offset
Which side of the source the new object lands on — picked by a click.
Mirror line
The two-point axis MIRROR reflects across.

Before you start

  • Have at least one drawn object (line, polyline, circle).
  • Turn OSNAP on so the mirror axis snaps to real geometry.
  • Decide the offset distance before starting OFFSET.

Step-by-step instructions

  1. 1
    Start the OFFSET command
  2. 2
    Type the offset distance
  3. 3
    Pick the object to offset
  4. 4
    Click the side
  5. 5
    Start MIRROR
  6. 6
    Define the mirror line

Visual reference

Common mistakes & fixes

  • Selecting an object before typing the distance in OFFSET.
    Fix: OFFSET asks for distance first — type the number, Enter, then pick.
  • MIRROR axis picked at random.
    Fix: Snap to real geometry (midpoint, endpoint) so the symmetry is exact.
  • Accidentally deleting the source in MIRROR.
    Fix: Press Y/N carefully at the final 'Erase source' prompt.

Troubleshooting

OFFSET says 'cannot offset that object'.Show
Cause: The source isn't supported (e.g. a block or hatch).
Fix: Explode it first, or use COPY with a typed displacement instead.
Mirrored text reads backwards.Show
Cause: MIRRTEXT is set to 1.
Fix: Type MIRRTEXT, Enter, set to 0 — text will stay readable after mirroring.

Practice exercise

Mirror half a butterfly
  1. Draw the left half of a butterfly outline with PLINE.
  2. Type MI, Enter. Select the polyline, Enter.
  3. Snap two points along the vertical axis of symmetry.
  4. Press N when asked to delete the source.
Success looks like: A symmetrical butterfly with both wings — the right side a perfect reflection of the left.

Pro tips & related commands

Pro tips
  • OFFSET has a Through option — type T to offset by clicking a point instead of typing a distance.
  • Set MIRRTEXT to 0 once per drawing so any mirrored text stays readable.
  • Use OFFSET on a closed polyline to create concentric inner/outer boundaries in one click.
Related commands
  • ARRAY(AR)
    Create rectangular or polar patterns of copies.
  • COPY(CO)
    Duplicate objects without parallel offset or reflection.
  • ROTATE(RO)
    Rotate objects around a base point.
Lesson quiz
0/2 correct

Score at least 2/2 to unlock lesson completion.

1. What do you type first inside OFFSET?
2. MIRROR needs which input?

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POLYLINE Deep-DiveFILLET + CHAMFER

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