upper u2153 to u00bc portion of the regulation height of the mailbox from the ground elastic 78 is stretchably mounted within post 28 by pins 36 and 38 the mailbox is aligned with axis 46 ball 48 is centered in groove 62 the mailbox can rotate 80 out of alignment with centerline 46 on vertical axis 70 on joint 30 when the mailbox is rotated out of alignment with centerline 46 groove 62 moves laterally away from ball 48 the mailbox will rotate when it is struck laterally in a direction adjacent to vertical axis 70 in fig3 post 28 is folded over as a result of a blow to the mailbox along line 40 of fig2 transverse to center line 46 center line 46 passes through ball 48 which is mounted on face 50 of joint 30 face 50 is generally normal to vertical axis 70 of post 28 groove 62 in face 54 of joint 30 also coincides with center line 46 when face 54 is resting on face 50 and groove 62 receives ball 48 when the mailbox is struck the mailbox and portion 68 of the post are thrown as one off from vertical axis 70 in fig4 post 28 is folded over as a result of a blow to the mailbox along direction line 72 of fig2 elastic element 78 is stretched when the faces 50 and 54 are moved apart by folding of the joint the faces are pulled back together by elastic element 78 when it resiles thus bringing post 28 in line with axis 70 elastic element 78 may be made of rubber metal coil or.