A surgical knife safety handle, comprising: a handle body having a distal end, a proximal end and a housing extending along a longitudinal axis between said distal and proximal ends, said housing defining a chamber therein and having at least one slot extending along said longitudinal axis accessing said chamber and having a first detent adjacent to said slot, said chamber being at least partially open at said distal end of said handle body; a knife holder extending from said distal end of said handle body along said longitudinal axis; a guard engaged with a guard positioning mechanism for longitudinal movement between a fully extended position and a fully retracted position with respect to said handle body, and said guard positioning mechanism slidably mounted in said chamber and having a user control mechanism extending from within said chamber via said slot and coupled with a user operable lock for engaging said first detent, and wherein said guard positioning mechanism is movable along with said guard between said fully extended position and said fully retracted positions, and said guard positioning mechanism further includes a position locking mechanism, characterized in that said guard has an enlarged distal end for at least partially enclosing a knife blade attachable to said knife holder; and the locking mechanism comprises: an integral cantilever beam and inclined projection opposite said user operable lock to engage a second detent at said fully extended position and to engage a third detent at said fully retracted position; and said chamber including said second and third detents (57, 55) to engage said integral cantilever beam and inclined projection as said guard positioning mechanism is slidably moved within said chamber between said fully extended position and said fully retracted position with respect to said handle body. a handle body having a distal end, a proximal end and a housing extending along a longitudinal axis between said distal and proximal ends, said housing defining a chamber therein and having at least one slot extending along said longitudinal axis accessing said chamber and having a first detent adjacent to said slot, said chamber being at least partially open at said distal end of said handle body; a knife holder extending from said distal end of said handle body along said longitudinal axis; a guard engaged with a guard positioning mechanism for longitudinal movement between a fully extended position and a fully retracted position with respect to said handle body, and said guard positioning mechanism slidably mounted in said chamber and having a user control mechanism extending from within said chamber via said slot and coupled with a user operable lock for engaging said first detent, and wherein said guard positioning mechanism is movable along with said guard between said fully extended position and said fully retracted positions, and said guard positioning mechanism further includes a position locking mechanism, characterized in that said guard has an enlarged distal end for at least partially enclosing a knife blade attachable to said knife holder; and the locking mechanism comprises: an integral cantilever beam and inclined projection opposite said user operable lock to engage a second detent at said fully extended position and to engage a third detent at said fully retracted position; and said chamber including said second and third detents (57, 55) to engage said integral cantilever beam and inclined projection as said guard positioning mechanism is slidably moved within said chamber between said fully extended position and said fully retracted position with respect to said handle body. an integral cantilever beam and inclined projection opposite said user operable lock to engage a second detent at said fully extended position and to engage a third detent at said fully retracted position; and said chamber including said second and third detents (57, 55) to engage said integral cantilever beam and inclined projection as said guard positioning mechanism is slidably moved within said chamber between said fully extended position and said fully retracted position with respect to said handle body.