You can use the Replace Face tool to directly modify complex, non-planar faces, even if they are imported or native. The tool extends or trims faces according to the new face you select. This tool extends or trims any face that you select; so, as its name suggests, the face you select is replaced by a new face.
For example, use this tool to attach a knob and a board. Attaching these bodies means that one face of the knob and one face of the board must be “glued together.” With the tool, you can replace the knob’s face with the board’s and ultimately create a complex body: a door.
Follow these steps to use Replace Face.
- Prepare two separate bodies, like a handle and pan.
You need to replace the face of one body with the face of the second body. - Go to Tools > Replace face.
- Select the face on the handle that you want to replace. This face, which is labeled with the tool badge, will be removed.
If you have selected the wrong face, then select the tool badge twice until the face you selected is no longer labeled with a badge. Then, select the correct surface. - Select the face (on the frying pan) that you will use to replace the handle’s surface. This face will be labeled with the target badge. The surface you replace will be extruded to meet the new surface.
Notice that since the Other Side switch is turned off, the replaced face doesn’t reach the other side of the pan.
If you want the replaced face to reach the other side of the pan, turn on the Other Side switch.
- Select Done to finalize the replacement. Or, if you want to start over, select Cancel.
When you use the Replace Face tool, try using the Other Side switch to create different kinds of bodies.
- Other Side switch: On
You can see in the edit mode and section view that the replaced face reaches the farthest side of the cylindrical body.
- Other Side switch: Off
The replaced face reaches the closest side of the cylindrical body.
💡Shortcut💡: If you select the face you want to replace first, the menu is customized automatically. From this adaptive menu, go to Menu > More > Replace face. 
When you’re done replacing faces, select Done.