I researched quite a lot into masturbation (not an imam or scholar) and my conclusion on it was makruh. I was wondering if it is worse to not use your hands e.g rubbing it on something. I do not want to do something wrong.
Allah made clear what is right (legal, halal, etc.) and what is wrong (illegal, haram etc.) in the qur'an. And for men or women the halal kinds of intercourse are mentioned too:
And they who guard their private parts (5)
Except from their wives or those their right hands possess, for indeed, they will not be blamed - (6) But whoever seeks beyond that, then those are the transgressors (23:5-7)
The last verse already should show that anything beyond intercourse between husband and wife (from today's perspective, as slavery is regarded as no more -legally- existing) is haram and has the same level!
And if somebody thinks the rule above only applies for men, the qur'an includes other verses including women too:
...the men who guard their private parts and the women who do so, ... ([33:35])2
Therefore if we understand masturbation as haram or in best case frowned upon it doesn't matter how and with whatever tools you practice or perform it. The ruling or qualification of the act would be the same.