Error when modifying rules file in debian packaging

Trying to get my debian packaging to work as I want, I modified the debian/rules file (showing line numbers)

12 %:
13  dh $@ 
14
15 override_dh_install:
16     dh_install
17     install -m 644 "My Company's Folder" "debian/mainproject/usr/share/MyCompanyFolder"

error:
.....
dpkg-buildpackage: host architecture i386
 dpkg-source --before-build mainproject-1.0
 fakeroot debian/rules clean
debian/rules:16: *** missing separator.  Stop.
dpkg-buildpackage: error: fakeroot debian/rules clean gave error exit status 2

For your particular debian/rules:16: *** missing separator. Stop. error, make sure you have tab characters in your debian/rules file. Spaces to indent do not work.