carrying a rucksack on his back

HI,
The man was carrying a rucksack on his back.Yes. However, I'd say 'had' would be a more common word than 'carried'. And in N. America, I seldom hear 'rucksack'. The common term is 'backpack'.
Is the above correct. Also, can I say:

"Take your rucksack on your back."? Sounds a bit odd. If you mean 'put it on your back', I'd say 'Put your backpack on'.

Clive

I know "rucksack" is an old use, although it is still commonly used in some places in the Indian sub-continent.

By the way, can I say "put your backpack on your shoulder."?

Hi,
Yes, but 'on your shoulder' is not the same as 'on your back'.

Best wishes, Clive

Thanks Clive.

Does "on your shoulders" mean slinging the backpack from the shoulders?

Hi,
Yes. But you said 'shoulder', which means one shoulder.
Best wishes, Clive

Thanks.

One more question. The plural "shoulders" does not change the meaning, does it?
Or does it mean that he is carrying two bags?

Hi,
The number of rucksacks depends on whether you say 'rucksack' or 'rucksacks'. It doesn't depend on whether you say 'shoulder' or 'shoulders'.
Clive

Got it. Thanks Clive.