
Knock around together
Informal
 This phrase is casual, more common in spoken or informal writing among friends or peers. 
Are you free to knock around together this weekend?
 Close Friendship
 Implies a friendly, often close relationship with the person you are spending time with. 
My cousin and I used to knock around together during holidays.
 No Specific Activity
 Used when the activities done together are not planned or organized; they're spontaneous and casual. 
We'd just knock around together, talking about everything.