3.2 Editing & Joining Polylines

PEDIT (Polyline Edit) is the primary command for modifying a polyline after it exists, and the ACU objectives call out Join specifically because it is the operation most likely to confuse candidates who assume any two touching objects will combine automatically. Understanding exactly what PEDIT requires — and what it silently refuses to do — is the difference between a clean single-object outline and a drawing full of disconnected fragments that only look connected.

Starting PEDIT: Polylines vs. Everything Else

When you run PEDIT and select an object that is already a polyline, AutoCAD immediately shows the polyline editing option list (Close/Open, Join, Width, Edit vertex, Fit, Spline, Decurve, Ltype gen, Reverse, Undo). But if you select a plain LINE or ARC instead, AutoCAD asks: "Object selected is not a polyline. Do you want to turn it into one? <Y>" Answering yes converts that single line or arc into a one-segment polyline, which is often the first step before joining more objects to it. This prompt is a frequent exam trap — candidates assume PEDIT only works on existing polylines, when in fact it can create one from a single line or arc as its starting point.

The Join Option: What "Touching" Actually Means

Once inside PEDIT with a polyline (or a line/arc you just converted) selected, typing J for Join lets you select additional objects — lines, arcs, or other polylines — to merge into the base object. Join succeeds only when the endpoints of the objects you add coincide exactly with an endpoint of the base object, within a small tolerance called the fuzz distance.

This "must touch end-to-end" rule is the single most tested trap in this objective. Two lines that look connected on screen because of visual overlap or a rendering artifact, but that were drawn from slightly different endpoint coordinates, will not join. The fix is to move or extend the objects so their endpoints truly coincide, or to increase the fuzz distance value when PEDIT prompts for one during a multi-object join.

PEDIT Multiple: Editing Several Polylines at Once

Before selecting an object, typing M for Multiple lets you pick several polylines (or lines/arcs) in one selection set and apply the same edit — most commonly Join, Width, or Close — to all of them simultaneously. When you choose Join after a Multiple selection, PEDIT prompts for a fuzz distance and then attempts to connect every object in the set wherever endpoints fall within that tolerance, which can merge several separate fragments into one polyline in a single pass. This is far faster than running PEDIT Join repeatedly on one base object at a time, and ACU scenario questions often describe cleaning up an imported or hand-drawn outline made of many small segments — Multiple plus Join is usually the efficient answer.

Close vs. Open: A Toggle, Not a Fixed Option

PEDIT's first-listed option changes label depending on the polyline's current state. On an open polyline, it reads Close and adds a new segment connecting the last vertex back to the first, setting the Closed property to Yes. Run PEDIT on that same polyline again, and the option now reads Open, which removes that closing segment and returns the polyline to an open state. Candidates sometimes expect a separate "Open" command; there isn't one — it is the same list position, relabeled based on the object's current Closed status.

Other PEDIT Options Worth Recognizing

• Width — sets one uniform width for every segment in the entire polyline, overriding any per-segment tapering.
• Edit vertex — opens a vertex-by-vertex submenu (Next, Previous, Break, Insert, Move, Straighten, Width, and more) for fine control over individual points.
• Fit — generates a smooth curve through every vertex using arcs.
• Spline — approximates a smoother curve using the vertices as control points.
• Decurve — reverses Fit or Spline, returning the polyline to its original straight-and-arc-segment form.
• Ltype gen — controls whether a non-continuous linetype generates continuously around the whole polyline or restarts at each vertex.

The Standalone JOIN Command

AutoCAD also offers JOIN as its own command, separate from entering PEDIT first. JOIN can combine collinear lines, concentric arcs, and end-to-end lines, arcs, and polylines into a single object directly, without the intermediate "turn it into a polyline?" prompt. For simple end-to-end cleanup, JOIN and PEDIT's Join option produce the same practical result; the exam may present either command name in a scenario, so recognize both as valid ways to merge touching objects into one.

On the Exam

Watch for questions describing objects that "appear connected" but fail to join — the correct answer usually points to a gap between endpoints or the need to adjust the fuzz distance, not a software error. Also expect a question testing whether you understand that exploding a polyline (with EXPLODE) breaks it back into separate line and arc entities and discards its width, which is the reverse of everything Join accomplishes.