Smeg SDR60XG3 - Manual (Page 13)

Instructions for the installer
33
6.3 Arrangement of burners on hob
BURNERS
1 Auxiliary
2 Semi-rapid
3 Rapid
4 Rapid
5 Ultra rapid
6.4 Lubrication of gas taps
After a while, the gas tap may become hard to turn or lock. If this
happens, it has to be cleaned inside and re-greased.
This must be done by a qualified technician.