Lesson 7: Modify

Modify

Learn how to change your drawing using tools like erase, move, copy, trim, and more.

You’ll find most of these tools in the Modify panel under the Home tab. Take a moment to explore that area in AutoCAD.

Erase

To delete something from your drawing, use the ERASE command:

• Type E in the command line, or
• Click the Erase tool on the ribbon

Your cursor will turn into a small square (called a pickbox). Click the objects you want to erase, then press Enter or the Spacebar.

Tip: You can also select objects first, before starting a command, and just press the Delete key. Many users do this because it’s faster.

Select Multiple Objects

If you need to select a lot of objects at once:

1. Click an empty spot (1)
2. Move the mouse left or right
3. Click again (2)

There are two ways this works:

• Crossing selection (green area): selects everything that touches or is inside the area
• Window selection (blue area): selects only what’s completely inside the area

This group of selected items is called a selection set.

Tip: To remove something from the selection, hold Shift and click the object you want to deselect. Then press Enter or Spacebar to continue.

Move and Copy

Example: Copying Tiles

Let’s say you want to copy a tile shape several times across a row. Start by drawing one tile (using a polyline).

• Click Copy, or type CP
• Select the object and press Enter

Now choose one of two methods:

Method 1: Distance

If the second tile needs to be exactly 10 inches away:

1. Click anywhere to set a base point (1)
2. Move the mouse to the right
3. Type 10 and press Enter again to finish

Method 2: Two Points

You can also copy by picking two points:

1. Start Copy and select the object
2. Click two points (like the two ends of the tile)

To add a small space between the tiles (like 1/8”), use the Move command:

• Click Move, or type M
• Select the new tile and press Enter
• Click anywhere, move to the right, and type .125 or 1/8

Tip: Your two reference points don’t need to be on the object—you can use any two points in the drawing.

Moving with Distance

1. Start Move
2. Select the object (1)
3. Click a base point (2) and a second point (3)
4. The object moves in the direction and distance between those two points

Creating Multiple Copies

You can repeat this process to make many evenly spaced copies.

1. Start Copy
2. Select the first circle
3. Click the center of circle 1, then the center of circle 2, and so on

For even more copies, try the Array option inside the Copy command. For example, if you’re placing columns or foundation piles, you can set how many you want and the spacing between them.

Offset

To create parallel lines or shapes, use the OFFSET command.

• Click Offset, or type O
• Select the object (1)
• Type how far you want the new line to be
• Click on the side where you want it to appear (2)

Tip: Use Offset to make concentric circles quickly.

Trim and Extend

These two tools help you clean up edges.

• TRIM cuts off parts you don’t need
• EXTEND stretches lines to reach another object

Start Trim or Extend by clicking the tool or typing TR or EX

Example: Extending Steps

1. Start Extend
2. Select the lines you want to extend
3. Press Enter
4. Click near the ends you want to stretch

This action causes the lines to extend up to the initial boundary they intersect.

You can also select multiple objects using:

• Fence (click two points to draw a crossing line)
• Freehand (click and drag across objects)

Trim works the same way, but you click the parts you want to remove.

Mirror

Mirror creates a flipped copy of objects across a center line.

Example: You want the right side of a bathroom to match the left side.

1. Start Mirror or type MI
2. Select the objects to mirror (use a window selection: 1 and 2)
3. Press Enter
4. Click two points (3 and 4) to define the mirror line
5. Press Enter again to keep the original objects

Tip: Look for symmetry! Mirroring can save you a lot of time.

Stretch

Stretch lets you change the length of parts of your drawing.

Example: You want to stretch a shape by 50 units:

1. Type STRETCH or S
2. Use a crossing window to select part of the shape (1 and 2)
3. Click a base point (3), move the mouse, and type 50

To shorten, move in the opposite direction.

Fillet

Fillet adds a rounded corner (arc) between two lines.

• Type FILLET or F
• Click the two objects you want to connect

Tip: Hold Shift when clicking the second object to make a sharp corner instead of a round one.

Explode

Explode breaks a compound object into separate pieces.

• Type EXPLODE or X

You can explode things like:

• Polylines
• Blocks
• Hatches

Once exploded, you can edit each part individually.

Edit Polylines

To change a polyline, use the PEDIT command:

• Type PE
• Select the polyline (or even a line or arc)

You can:

• Join separate lines into one polyline
• Change the width
• Convert lines/arcs to polylines

Tip: Sometimes it’s easier to explode a polyline, edit the parts, then re-join them using PEDIT.

Grips

Grips are little blue squares that appear when you select an object (without starting a command).

You can:

• Click a grip
• Drag it to a new spot
• Click again to finish

By default, this starts Stretch mode. Press Enter to switch to other edit modes. Some users do a lot of quick edits just using grips!