Ok, i think you have to steal your friend's secret base flag to move them. I'm not 100% sure but good luck!
-Tim get the HM STRENGTH in the lost tower and teach it to a pokemon.you don't have to steal anything.and i am 100% sure
-------------------------------------------- To move rocks in secret base, steal your friend's base flag. For in-game rocks HM ROCK SMASH or HM STRENGTH should work. Rock Smash is a half-crumbled rock while Strength is a boulder. the second guy is right
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you can use the hm strength you can smash rocks with rock smash
Teach the HM Rock Smash to a Pokemon and interact with the rock. Round rocks need the move strength and not all Pokemon can use these moves.
get the HM strength, and teach it to a Pokemon
Any Pokemon able to learn the HM strength can move boulders. To shatter rocks you need the HM Rock Break.
you can buy it in veilstone