7.2 Move, Copy, Rotate, Mirror, Scale & Stretch

MOVE, COPY, ROTATE, MIRROR, SCALE, and STRETCH make up the core set of transform commands tested under ACU Objective 3.2 — the tools that take existing geometry and relocate, duplicate, rotate, flip, resize, or reshape it. All six share a common structural idea even though their specific prompts and options differ: each depends on a base point that anchors the operation, and the exam tests both the mechanical prompt sequence for each command and a handful of option-driven nuances that are easy to overlook.

Base Point: The Anchor for Every Transform

A base point is the reference location a command uses to calculate its result. For MOVE and COPY, the base point is the spot that travels to wherever you specify next — think of it as picking up an object by one specific handle. For ROTATE and SCALE, the base point instead stays perfectly still while everything else pivots or resizes around it — it's the pin the rest of the operation turns or grows around. Choosing a meaningful base point (an object's corner, its center, an endpoint) rather than an arbitrary empty spot on screen is what makes these commands produce clean, predictable, precise results instead of rough approximations.

MOVE: Relocate, Nothing Left Behind

MOVE (alias M) prompts for Select objects, then Specify base point, then Specify second point (or a displacement). Typing coordinates or using an object snap for both points relocates the selection by the exact distance and direction between them. If you press Enter at the second-point prompt instead of picking a point, AutoCAD treats whatever you typed at the base-point prompt as a direct displacement value rather than a point — typing @3,2 as the base point and pressing Enter twice moves the selection 3 units in X and 2 units in Y, with no true base-point location involved at all. Only the objects you selected move; nothing is left behind at the original location.

COPY: Same Prompts, Original Stays

COPY (alias CO or CP) uses the identical Select objects → base point → second point sequence as MOVE, but the original objects remain exactly where they started while a duplicate appears at the new location. Current AutoCAD releases default COPY to Multiple mode: after placing the first copy, the command keeps prompting for another second point, letting you stamp out several copies of the same selection in one command run without restarting COPY each time. Typing O for the Modes option lets you switch to Single, which places exactly one copy and ends the command immediately — useful when you specifically want to avoid accidentally leaving the command active for repeated placements.

ROTATE: Base Point Plus Angle, or Reference

ROTATE (alias RO) prompts for Select objects, Specify base point, then Specify rotation angle. A positive angle rotates counterclockwise around the base point under AutoCAD's default angle direction, matching the same counterclockwise convention used for polar coordinate entry. The Reference option, typed as R at the angle prompt, solves a different problem: instead of knowing how many degrees to rotate, you know the object's current angle and the exact final angle you want it to end up at. Reference asks for a reference angle (typed, or picked as two points along the object's current alignment) and then a new angle; AutoCAD calculates the difference and applies exactly that much rotation. This avoids manual angle subtraction when aligning a misplaced detail to a fixed drawing feature.

MIRROR: The Erase-Source Prompt

MIRROR (alias MI) prompts for Select objects, then Specify first point of mirror line, then Specify second point of mirror line — these two points define an invisible axis the selection flips across. After the mirror line is set, AutoCAD always asks Erase source objects? [Yes/No] <N>:, defaulting to No. Accepting the default keeps the original objects in place and adds a new mirrored copy; typing Y deletes the originals so only the mirrored result remains, effectively flipping the objects in place rather than duplicating them. One related system variable worth knowing: MIRRTEXT, when set to 0 (the default), keeps mirrored text readable left-to-right instead of flipping it backward, while setting it to 1 mirrors text exactly like any other geometry, producing backward, mirror-image text.

SCALE: Base Point Plus Factor, or Reference

SCALE (alias SC) prompts for Select objects, Specify base point, then Specify scale factor. The base point stays fixed while the selection grows or shrinks uniformly around it — a factor greater than 1 enlarges the selection, a factor between 0 and 1 shrinks it. Just like ROTATE, SCALE offers a Reference option (typed R) for situations where you know a current length and a target length but not the numeric ratio between them: specify the reference length (by picking two points or typing a value) and then the desired new length, and AutoCAD computes and applies the correct scale factor automatically — a wall segment currently 8 units long that needs to become 10 units long scales by a factor of 1.25, without you ever typing 1.25 yourself.

STRETCH: The One That Needs a Crossing Selection

STRETCH (alias S) is the odd one out because its selection method changes what it actually does. STRETCH requires selecting objects with a crossing window or crossing polygon (dragging right-to-left, or typing C or CP) rather than a standard left-to-right window. Only the vertices or endpoints that fall inside the crossing boundary move to the new location; any endpoint left outside the boundary stays fixed, which is what reshapes a line or polyline instead of relocating it wholesale. An object entirely enclosed within the crossing selection — every one of its points inside the boundary — moves as a whole, exactly like MOVE, since there's no partial vertex left behind to anchor it. Objects like circles and blocks behave the same way: since a circle's defining point for this purpose is its center rather than any point on its circumference, a circle only ever moves whole (if its center is inside the crossing window) — it's never reshaped or resized by STRETCH.

Worked Example

A door opening drawn as two parallel jamb lines needs to widen by 6 inches. Selecting only the jamb line to move with a crossing window that captures just that line's near endpoint — leaving its far endpoint, which connects to an unrelated wall corner, outside the boundary — and running STRETCH with a base point at the captured endpoint and a second point 6 inches further out, lengthens the opening cleanly without disconnecting the wall corner the other endpoint relies on.

On the Exam

Expect direct recall of each command's prompt sequence and its distinguishing option — COPY's Multiple default, ROTATE and SCALE's Reference option, MIRROR's Erase Source default, and above all, STRETCH's crossing-selection requirement and its different treatment of circles and blocks versus line endpoints. Scenario questions often describe a selection method (a plain window vs. a crossing window) and ask you to predict whether STRETCH will reshape, relocate, or ignore the selected geometry.