4th Gen how to evolve rhydon?

[Storm-DC]

title pretty much says it all. i want to add that i do know about that protectorthingy, but don't know what to do with it. let him hold it and trade?

 

[DarkDragonite12]

Let Rhydon hold the "Protector" Item, and then trade him to a friend, just as evolving Kadabra/Machoke/Haunter.

And remember to trade it back, lol. ;)

 

[Midnight Beat]

BTW if you need to know where you get it, it is at the start of the sandstorm.

 

[Caleb290]

if you dont have a friend to trade to you can deposit it in the GTS and then go complete any trade like for some bidoof or something and then go take rhydon out it will evolve but I do not know where the item is :(

 

[DarkDragonite12]

but I do not know where the item is :(

The item also found on Route 228(It is in the Shape of a Poke ball)where Rhyhorn/Rhydon are found.

 

[Storm-DC]

can the item be used only once?

i already have it, but i am still looking for the magnamizer(?) for electabuzz and a water stone, where are those?

 

[Virtual Headache]

can the item be used only once?

i already have it, but i am still looking for the magnamizer(?) for electabuzz and a water stone, where are those?

Yes.

You might mean the Electrizer, the Magmarizer is used for evolving Magmar. Some wild Elekid will hold it.
Water stones can be found in the underground, but are kinda rare.