diff --git a/tools/build_flash_erase_lock.bat b/tools/build_flash_erase_lock.bat
new file mode 100644
index 0000000..0019148
--- /dev/null
+++ b/tools/build_flash_erase_lock.bat
@@ -0,0 +1,61 @@
+@echo off
+setlocal enabledelayedexpansion
+
+REM ==============================================================
+REM  Build + Flash + APPROTECT lock  (PRODUCTION ONLY)
+REM  - Rebuilds so build\merged.hex is up to date, then flashes.
+REM  - Do NOT run on development boards (locking needs --recover).
+REM ==============================================================
+
+set "REPO=%~dp0.."
+set "BUILDDIR=%REPO%\build"
+set "HEX=%BUILDDIR%\merged.hex"
+
+REM cmake from the nRF Connect toolchain, fallback to PATH
+set "CMAKE=C:\ncs\toolchains\fd21892d0f\opt\bin\cmake.exe"
+if not exist "%CMAKE%" set "CMAKE=cmake"
+
+echo [FLASH] FULL ERASE + APPROTECT LOCK mode (production)
+echo [FLASH] This wipes application flash, NVS/settings, and BLE bonds.
+echo [FLASH] After locking, SWD debug read/write is disabled.
+echo [FLASH] To unlock later: nrfjprog --recover (mass-erases the chip).
+echo [FLASH] DFU(SMP) over BLE still works after locking.
+echo.
+
+REM --- Step 1: build (updates merged.hex) ---
+echo [FLASH] Step 1/4: build (update merged.hex)
+"%CMAKE%" --build "%BUILDDIR%"
+if errorlevel 1 (
+    echo [FLASH] Build FAILED. Aborting.
+    exit /b 1
+)
+
+if not exist "%HEX%" (
+    echo [FLASH] merged.hex not found: %HEX%
+    echo [FLASH] Build the project first.
+    exit /b 1
+)
+echo [FLASH] Using: %HEX%
+echo.
+
+REM --- Step 2: chip erase + program + verify ---
+echo [FLASH] Step 2/4: chip erase + program + verify
+nrfjprog --program "%HEX%" --chiperase --verify --reset
+if errorlevel 1 (
+    echo [FLASH] Program FAILED. Aborting before lock.
+    exit /b 1
+)
+
+REM --- Step 3: enable APPROTECT ---
+echo [FLASH] Step 3/4: enabling APPROTECT (readback protection)
+nrfjprog --rbp ALL
+
+REM --- Step 4: pin reset to apply protection ---
+echo [FLASH] Step 4/4: pin reset
+nrfjprog --pinreset
+
+echo.
+echo [FLASH] Done. POWER-CYCLE the device to fully latch APPROTECT.
+echo [FLASH] Verify lock: nrfjprog --memrd 0x0  should now FAIL.
+endlocal
+pause