earth straps

No, they probably mean clean up the mating surfaces with abrasive paper to make a good metallic contact, bolt up & put something like grease or anti corrosion spray on the ends of the straps to stop corrosion & the ingress of moisture,

Steve.

might stop it going rusty which would effect it.....

I always make a point of fitting a secondary earth strap regardless of the condition of the original,, this practice was first advised to me as an apprentice working for a BMC/jag/Rolls dealer a long time ago, Fitzy

Another is to place a new shakeproof washer between the strap and the body. (not under the nut)