The US Attorney's Office said Carlos Rodriguez-Cruz, 33, punched a guard at FCI Schuylkill in Minersville last Oct. 6.
According to authorities, the guard found a homemade knife or "shank" during a search of Rodriguez-Cruz's cell.
Rodriguez-Cruz, formerly of Puerto Rico, faces up to eight years of imprisonment, supervised release, and a fine.
The guilty plea comes just a week after another FCI Schuylkill inmate pleaded guilty to assault with a deadly weapon against a different prisoner. In that case, prosecutors said 36-year-old Jared Sebaugh "assaulted another inmate with a prison-made weapon consisting of a combination lock attached to a cloth strap."
Click here to follow Daily Voice Allentown and receive free news updates.