: Ensure the Merge result checkbox is selected in your feature properties if you want the new feature to combine with an existing solid body.

Check the option to convert the patched enclosure into a solid immediately.

: Used when multiple surfaces enclose a volume. Go to the Surfaces tab and select Knit Surface . Select all the surfaces that form the closed volume.

Check the box in the property manager. If the surfaces perfectly enclose a space, SOLIDWORKS will automatically convert it into a single solid body.

: If a solid fails to form, your surfaces may have small gaps or "naked edges." Use the Check tool (under Evaluate) to find "Open surfaces" or "Invalid faces."