lower horizontal edge of locking tab 75 is adjacent the horizontal edge of indention 76 to prevent fin 73 from moving upward thereby firmly securing fin 73 inside fin box 71 in fig1 the surfer has bent locking arm 70 by pressing against its upper portion with his finger indention 76 has been cleared from locking tab 75 enabling the surfer to remove the fin a fourth preferred embodiment is shown in fig1 and 20 in the fourth preferred embodiment locking arm 80 is connected to fin box 81 fin 83 is installed in a fashion similar to that described above for the earlier preferred embodiments as fin 83 is lowered into fin box 81 locking arm 80 bends allowing fin 83 to be inserted inside fin box 81 in fig1 fin 83 is fully inserted inside fin box 81 locking arm 80 has snapped back to its upright position the upper horizontal edge of locking tab 85 is adjacent the horizontal edge of indention 86 to prevent fin 83 from moving upward thereby firmly securing fin 83 inside fin box 81 in fig2 the surfer has bent locking arm 80 by pressing against its upper portion with his finger indention 86 has been cleared from locking.