Offset, trim, extend and fillet walls

What you will make

A small room with 200-thick walls: the inside face is drawn, the outside face is offset, the corners are cleaned up, and a doorway is cut through one wall.

Draw the inside face

1. Type L and press ReturnEnter.
2. Type 0,0 and press ReturnEnter.
3. Type @5000,0 and press ReturnEnter.
4. Type @0,4000 and press ReturnEnter.
5. Type @-5000,0 and press ReturnEnter.
6. Type C and press ReturnEnter.
7. Click Extents.

You have four separate lines. (A closed polyline would offset in one go; separate lines show how Fillet cleans corners.)

Offset the outside face

1. Type O and press ReturnEnter. The prompt reads Specify offset distance [Through] <Through>:.
2. Type 200 and press ReturnEnter.
3. At Select object to offset, click the bottom line.
4. At Specify point on side to offset, click anywhere below it. A parallel line appears 200 below.
5. Click the right line, then click to its right.
6. Click the top line, then click above it.
7. Click the left line, then click to its left.
8. Press ReturnEnter to end the command.

You should see four outer lines, each the same length as its inner line, so the outer corners do not meet.

OFFSET works on lines, arcs, circles and polylines. Offsetting a closed polyline offsets the whole outline, corners included.

Clean up the outer corners with Fillet

FILLET joins two lines at a corner: it trims or extends both so they meet. With a radius of 0 the corner is square.

1. Type F and press ReturnEnter. The prompt reads Select first line [Radius]:.
2. If the last fillet you did used a radius, type R, press ReturnEnter, type 0 and press ReturnEnter.
3. Click the outer bottom line near its right end.
4. At Select second line, click the outer right line near its bottom end.

The two lines now meet in a sharp corner, and the command ends.

1. Press ReturnEnter to repeat FILLET, and do the next corner.
2. Repeat until all four outer corners meet.

Click each line on the part you want to keep. With a radius above 0, Fillet adds an arc between the lines instead.

Cut a doorway with Trim

First draw the two door jambs across the bottom wall, then trim the wall lines between them.

1. Type L and press ReturnEnter.
2. Type 1000,200 and press ReturnEnter.
3. Type @0,-600 and press ReturnEnter, then press ReturnEnter again.
4. Press ReturnEnter to repeat LINE.
5. Type 1900,200 and press ReturnEnter.
6. Type @0,-600 and press ReturnEnter, then press ReturnEnter again.

You now have two short lines crossing the bottom wall 900 apart.

1. Type TR and press ReturnEnter. The history says "Every object is a cutting edge. Pick the part to remove."
2. Click the inner bottom line between the two jambs. That piece disappears.
3. Click the outer bottom line between the two jambs. That piece disappears too.
4. Click the part of each jamb that sticks out above the wall, and the part below it.
5. Press ReturnEnter to end the command.

You should see a 900 opening in the bottom wall, with the jambs closing the wall ends.

In CadCraft, Trim does not ask you to choose cutting edges first: every visible object is a cutting edge. Pick the piece you want gone. Type U and press ReturnEnter to put back the last piece without leaving the command.

Extend a line to meet another

EXTEND lengthens a line, arc or polyline end until it meets the next object in that direction.

1. Type L and press ReturnEnter.
2. Type 1000,2000 and press ReturnEnter.
3. Type @2000,0 and press ReturnEnter, then press ReturnEnter again. The line stops 2000 short of the right wall.
4. Type EX and press ReturnEnter.
5. Click the new line near its right end.
6. Press ReturnEnter to end the command.

The line now runs to the inner face of the right wall. Every visible object is a boundary; pick near the end that should grow.

Common mistakes

• "Nothing crosses that object there." Trim found nothing crossing the piece you picked. Check that the cutting line really crosses it (zoom in), and that it is not on a layer that is off.
• "No boundary in that direction." Extend found nothing to run into. Pick nearer the end that should grow.
• "Fillet works on lines so far." Fillet only joins lines. For polylines, explode them first, or draw the corner again.
• "Those lines are parallel, or the radius is too large." Fillet cannot make a corner between parallel lines, or the radius does not fit.
• The offset went to the wrong side. The side is where you click after picking the object. Undo with ⌘ZCtrl+Z and click on the other side.
• "Cannot offset that far." The offset would turn the arc, circle or polyline inside out. Use a smaller distance.