ridged type surface is merely illustrative as best seen in fig5 the thumb grip 22 has an arcuate shape arcuate shapes provide an ideal shape for adapting to the thumb of the user and for providing the forces for moving the hammer lock 3 between the locked and unlocked positions within the top surface 22 a shaft recess 25 is formed and holds the keyed locking shaft 21 see fig4 and 6 the shaft recess 25 extends through to the bottom of the hammer lock 3 as shown in fig5 a bottom 26 of the keyed locking shaft 21 can extend beyond and be retracted from a bottom of the base 8 of the hammer lock 3 in this manner in a locked position the bottom 26 of the keyed locking shaft 21 engages into the first shaft hole 20 and prevents the hammer lock from being slide the first shaft hole 20 and the bottom of the keyed locking shaft 21 are adapted to each other for locking the hammer lock 3 in position in the unlocked position the keyed locking shaft 21 may be housed completely within the shaft recess 25 in addition the keyed locking shaft 21 may be secured in the second shaft hole 31 in a secured unlocked position the keyed locking shaft 21 is moved within the.