the guard rail support attachment and positioning block or spacer block is used to space guard railing away from posts such as “ i ” beams which are driven into the ground . the spacer block keeps automobile wheels from impacting the i beams and initiating a roll of the vehicle . the spacer block is a generally rectangular block or cube including corded - out cavities to reduce weight and tabs or projections which cooperatively engage the side of the post and the edge of the guard rail to position and hold same in position for attachment with holding members such as bolts . webbing can be used to provide structural support within the cavity . the spacer block may be formed by low pressure injection molding to form a structural foam spacer block to optimize the strength to weight characteristics of the spacer block . the spacer block may be formed of a virgin and / or recycled plastic material and / or include virgin or recycled rubber material such as from obtained from the regrind of used tires and / or another elastomeric material from other sources .