If you're working on a 3D model in Blender and need to export it as an Obj file, the process is fairly straightforward. Here's a step-by-step guide on how to save as an Obj in Blender:

1. Finalize your 3D model: Before exporting your model as an Obj file, make sure that it is complete and ready for use in other applications or for sharing with others.

2. Select your model: In Blender, select the 3D model that you want to save as an Obj file.

3. Go to File > Export > Wavefront (.obj): Once your model is selected, navigate to the File menu at the top of the Blender interface. Then, hover over the Export option and select Wavefront (.obj) from the dropdown menu.

4. Adjust export settings: After selecting the Wavefront (.obj) option, a settings window will appear. Here, you can adjust various export settings such as object scale, smoothing groups, and more based on your specific needs. Make sure to review and adjust these settings to match your requirements.

5. Choose export location: Once the export settings are adjusted, select the destination folder where you want to save your Obj file. Give your file a name and click 'Export OBJ' to save your 3D model as an Obj file.

6. Check your exported file: After the export process is complete, navigate to the folder where you saved your Obj file and open it to ensure that it has been exported correctly. You can also import the Obj file into another 3D modeling software to verify its integrity.

By following these steps, you can successfully save your 3D models as Obj files in Blender, allowing you to use them in a wide range of applications and share them with others in the 3D modeling community.