Is is possisble to gain (muscle) mass from body weight exercises?

I currently do not have a gym membership for the summer. Was lifting 4-5 times a week during the year at college.

Am I correct that body weight exercises cannot allow you to make (much if any) real gains?
Updates
+1 y
just found a gym to join, so looks like I'll be doing that. good info though.
Is is possisble to gain (muscle) mass from body weight exercises?
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