For years I have seen all kinds of neat lil gadgets and hacks to aid in driving nails without smashing one’s fingers, and I chuckle at them all. The problem with hammering fingers from a missed hammer blow is caused by two factors: poor hammer technique and holding a nail “pinched” between one’s forefinger and thumb.
The “appropriate technology” for preventing smashed finger/thumb is present on almost everyone’s own hands. Simply turn the hand used to hold the nail for starting palm up and hold the nail between the index and middle fingers. Even if one misses the nail strike, a starter blow (should be a light tap) will not hit bone and fingernails directly but a cushion of flesh.
In the decades I have used this technique, since being shown by my paternal grandfather, I’ve not even had any noticeable bruising in the few times I’ve missed an initial hammer strike.
And yeh, few times. PRACTICE MAKES PERMANENT (or nearly so, at least). Practicing holding a hammer correctly, striking correctly, holding nails correctly: all these make for a much better experience, and not just in lessening injuries from missed initial hammer strikes but also in lessening fatigue during long (whatever “long” is to the user *heh*)sessions hammering nails.
Sometimes, the appropriate technology is right at the end of one’s arms.