Function Syntax: ExtendStartEndMultiple Version: 1 Date: 01.08.2026 AI+https://www.lee-mac.com/doubleextend.html Description 🧩 Lengthen is an enhanced Double Extend style AutoLISP tool for extending multiple selected LINE ARC LWPOLYLINE and POLYLINE entities at both ends. 🎛️ The DCL first workflow includes object picking highlighting separate Start and End extension values a Both Ends Slot option dynamic drag preview Apply Undo Debug OK and Cancel. 🧪 The file also provides DEX and DEXDEBUG aliases for the main tool and its diagnostic report. Function Syntax Main command: ExtendStartEndMultiple Alias: DEX Debug command: DEXDEBUG SEO Optimized Overview 🎛️ The dialog opens before object selection and includes Pick Entities Window Crossing. ➡️ Extend Start and Extend End control independent endpoint extension values. ↔️ Enable Both Ends Slot activates one shared slot length that can be used on both ends. 👁️ Dynamic Drag Preview lets the user interactively adjust the both ends slot while selected objects remain highlighted. ✨ Selected entities are highlighted while the tool is active and restored when appropriate. ✅ Apply performs the current operation and keeps the tool available for further adjustment. ↩️ Undo restores the snapshot taken before the latest Apply style operation. 🧪 Debug writes a DEX_debug.txt diagnostic report into the AutoCAD TEMP folder. 💾 The dialog stores its last screen relative position in a session global. 🛡️ The header identifies the file as Civil 3D compatibility updated. Primary Workflow • Run DEX or ExtendStartEndMultiple. • Use Pick Entities to select LINE ARC LWPOLYLINE or POLYLINE objects. • Enter Extend Start and Extend End values. • Optionally enable the Both Ends Slot and set its slot length. • Use Dynamic Drag Preview to adjust the shared slot interactively. • Use Apply and Undo while tuning the result. • Use Debug when a diagnostic report is needed. • Use OK to commit the final geometry or Cancel to restore the starting snapshot. Functionalities ✅ DCL first workflow - opens the interface before source selection. ✅ Pick Entities button - supports window crossing pick fence and All selection methods. ✅ Selection highlighting - keeps selected geometry visually highlighted. ✅ Separate endpoint values - controls start and end extensions independently. ✅ Both Ends Slot - applies one shared extension value to both ends. ✅ Dynamic drag preview - updates the shared slot through cursor movement. ✅ Apply - updates the selected geometry without closing the dialog. ✅ Undo - restores the latest stored geometry snapshot. ✅ Debug report - writes settings selection and entity information to DEX_debug.txt. ✅ Dialog position memory - stores the DCL screen position during the AutoCAD session. ✅ C3D compatibility - includes protected Visual LISP COM initialization and command-s cleanup. Important Commands and Aspects 🧩 DEX:snapshot and DEX:restore preserve source entity state. 🧩 DEX:dynamic-both implements the interactive slot drag preview. 🧩 LM:dex:run applies the underlying endpoint extension geometry. 🧩 DEX:debug writes the diagnostic text report. Result 🎯 The result is selected curve geometry extended at the start end or both ends according to the current DCL settings. 👁️ The interactive preview and rollback workflow is designed for rapid trial and adjustment. Important Notes ⚠️ The DCL title is Double Extend even though the file is named Lengthen. ⚠️ The main callable commands are ExtendStartEndMultiple DEX and DEXDEBUG. ⚠️ Debug output is written to the AutoCAD temporary directory. ⚠️ Cancel restores the initial snapshot when one has been created. SEO Keywords 🏷️ AutoCAD, 🏷️ Civil 3D, 🏷️ AutoLISP, 🏷️ Lengthen, 🏷️ DEX, 🏷️ Double Extend, 🏷️ ExtendStartEndMultiple, 🏷️ Dynamic preview, 🏷️ Apply, 🏷️ Undo, 🏷️ Debug, 🏷️ Polyline extension, 🏷️ DCL