Editing: where CAD earns its keep

Here's a trade secret: drafters don't draw most of their lines. They copy, offset and trim them into existence from lines that already exist. Editing isn't cleanup — it IS the workflow. This lesson gives you the big five.

Every modify command follows the same conversation: command → select things → Enter to confirm selection → answer the questions. (That middle Enter — "I'm done selecting" — is the step beginners forget, then wonder why nothing's happening. The command line, as always, is telling you.)

1. MOVE (M) — relocate exactly

1. 1M, Enter → select your desk rectangle → Enter
2. 2"Specify base point:" — click a corner of the desk (snap!)
3. 3"Specify second point:" — click where that corner should land — or better, Ortho on, point a direction, type 500: the desk moves exactly 500mm that way.

The base point idea matters: you're picking the "handle" you carry the object by. Grab a corner, place a corner — precise moves come from precise handles.

2. COPY (CO) — the duplicate machine

Identical conversation to MOVE, except the original stays. Bonus: it keeps offering "Specify second point:" again and again — one command, six chairs. Enter when done.

Need a row of desks 1500 apart? Copy with Ortho on, type 1500, 3000, 4500 at successive prompts. Exact spacing, zero measuring.

3. OFFSET (O) — the parallel factory

The most drafting-flavoured command of all:

1. 1O, Enter
2. 2"Specify offset distance:" — type 230 (a brick wall's thickness), Enter
3. 3Click the line to offset
4. 4Click which SIDE the copy should appear
5. 5It keeps going — offset more lines, or Enter to finish.

Walls in real floor plans are drawn exactly this way: outline once, OFFSET 230, done — every wall two perfectly parallel lines.

4. TRIM (TR) — the scissors

After offsetting and crossing lines, corners overshoot — lines poking past where they should stop. TRIM cuts them back:

1. 1TR, Enter, then Enter again (that second Enter means "everything is a cutting edge" — the modern default and what you want)
2. 2Click the poking-out bits. They vanish up to the nearest crossing line.
3. 3Enter to finish.

Its sibling EXTEND (EX) does the reverse — lengthens a line to meet another. Trim the overshoots, extend the undershoots: between them, every sloppy junction becomes a crisp corner.

5. ERASE (E) and the sacred UNDO

E, Enter, select, Enter — gone. (Or select first, press Delete.)

And the command that makes learning possible:

This is why CAD beats paper for learners, not just professionals: every experiment is free. Try the weird thing. Ctrl+Z is right there.

Selection: one skill, two directions

When any command says "Select objects:", drag a box — and direction changes meaning:

• Drag left → right (blue box): selects only what's COMPLETELY inside — surgical
• Drag right → left (green box): selects anything the box even TOUCHES — generous

Blue for precision, green for "grab all that". This tiny distinction saves professionals hours weekly; learn it now and it's free forever.

The capstone exercise

In room-practice.dwg, using ONLY what you've learned:

1. 1OFFSET the room rectangle 230 inward — your room now has proper walls
2. 2COPY the desk twice, exactly 1500 apart (Ortho + typed distance)
3. 3MOVE the stool to sit exactly at the middle desk's midpoint (base point: stool centre; landing: midpoint snap)
4. 4Draw two crossing lines anywhere, TRIM them into a neat corner, then ERASE the leftovers

Finish that and you possess the honest core of AutoCAD: exact drawing, exact connecting, exact editing. Modules 2 and 3 add layers, dimensions, text and real floor plans — but they're arrangements of what you can already do.