Function Syntax: EXTENDTOBLOCK_ / EXTENDTOBLOCK / ETB Version: 1.1 Date: 20.07.2026 6:57:05AM N/A 🚀 ExtendToBlock_003 ExtendToBlock_003 is an AutoCAD and Civil 3D 2024 .NET utility with a modeless C# interface for previewing and selectively extending curve endpoints to selected block references. It improves CAD editing accuracy by detecting only relevant curves, testing them against real exploded block geometry, and showing the proposed endpoint and extension distance before any checked object is modified. Main Commands 🧰 Run EXTENDTOBLOCK_003 to start the collision-safe build-specific command. ⚙️ Run EXTENDTOBLOCK as the stable full-name convenience alias. ⚡ Run ETB as the short convenience alias. SEO Optimized Description 📐 This AutoCAD extend-to-block tool finds lines, lightweight polylines, arcs, and splines whose loose endpoints can reach selected block references and presents the results in a reviewable modeless grid. 🔍 The utility supports CAD cleanup, symbol connection, utility drafting, schematic editing, Civil 3D production, endpoint correction, block connection, and workflows where curves must terminate precisely on block geometry. 🧠 It recursively explodes selected blocks and nested blocks into temporary curve geometry, calculates extended intersections, identifies the nearest Start or End point, and uses the block frame only as a fallback when real curve geometry is unavailable. 📌 ExtendToBlock_003 is useful for CAD technicians, Civil 3D users, survey drafting, utility plans, network diagrams, construction details, electrical layouts, mechanical symbols, and repetitive endpoint-extension tasks. Functionalities 🚀 Modeless C# workflow - opens a resizable Windows Forms interface that remains available while users review blocks, candidates, previews, and logs. 🧱 Multiple target blocks - uses preselected block references or prompts for one or more INSERT entities. ☑️ Target block controls - groups blocks by effective name and lets users enable all, disable all, or individually process block-name groups. 🎯 Real block geometry - tests candidate curves against recursively exploded constituent curves from the block and nested blocks instead of snapping only to an invisible bounding rectangle. 🟧 Frame fallback - retains the target block bounding frame as a fallback intersection target when no usable exploded curve geometry is available. 📐 Supported Apply objects - modifies LINE, LWPOLYLINE, ARC, and SPLINE entities. ℹ️ Heavy polyline visibility - detects AcDb2dPolyline and AcDb3dPolyline candidates but lists them as unsupported informational rows in this build. 🔍 Relevant candidate scanning - lists only curves that already reach the block or whose extension intersects the target geometry. 🚫 Closed-curve filtering - skips circles, closed polylines, full ellipses, and other curves without a loose endpoint. 📋 Detailed candidate grid - shows type, status, layer, handle, Start or End choice, extension distance, target block name, block handle, and a full description. 🟢 Visual preview - draws the candidate curve, actual block geometry, reference frame, original endpoint, proposed new point, and dashed extension segment. ✨ Viewport highlighting - highlights selected target blocks or the active candidate entity in AutoCAD and provides a Clear Highlight control. ✅ Selective application - modifies only rows checked in the YES/NO column and prevents informational rows from being selected. 🔄 Apply and OK behavior - Apply performs the confirmed extension and keeps the form open, while OK performs the same operation and closes the form. ↩️ Undo Apply - restores the latest Apply operation from the active dialog session using saved clones of the original entities. 🛡️ No-selection warning - explains that a row must be checked before Apply and asks for confirmation before OK closes without changing geometry. 📝 Diagnostic logging - records command activity, target blocks, candidates, handles, layers, statuses, extension distances, and apply results. 📋 Copy and save log - copies the live log to the Windows clipboard or saves a timestamped diagnostic TXT file. 💾 Persistent settings - saves form position, form size, and per-block-name process choices in ExtendToBlock.cfg. 🧪 Side-by-side test builds - uses a generated build number in the DLL and primary command so multiple NETLOADed versions can coexist in one AutoCAD session. Practical Result ✅ The result is a controlled AutoCAD endpoint-extension workflow that finds applicable curves, previews the proposed geometry, and extends only the checked supported objects to the selected block content. This makes ExtendToBlock_003 useful for block connection, CAD production cleanup, symbol-based drafting, Civil 3D support drawings, utility networks, and repetitive curve-end correction. Important Note This command directly modifies checked drawing curves. Review the target block, status, Start or End choice, extension distance, and visual preview before applying. Closed curves are skipped, heavy 2D and 3D polylines are not auto-applied in build 003, long extension distances are not capped, spline changes move a terminal point rather than fully refitting the curve, and Undo Apply is available only for the latest Apply while the dialog remains open.