A trellis support system comprises a vertical post comprising a front portion and first and second opposing side wall portions, the front portion comprising an aperture, the aperture comprising a first portion and a second portion adjacent the first portion, and a horizontal cross arm perpendicular to the vertical post comprising a front portion and first and second opposing side wall portions dimensioned to match the front and side wall portions of the post, the front portion comprising a tab member dimensioned to engage the first portion of the aperture and a lock member positioned adjacent the tab member and dimensioned to engage the second portion of the aperture.
