Left hand scissors and needle holders allow left-handed people:
To be as precise as right-handed users, especially in delicate applications when results are critical.
To use natural actions without a second thought.
To use instruments with smooth, even action.
To have the maximum control of their instruments.
Up to 10% of the world's population is left-handed, yet most instruments are built for right-handed people. Instruments like scissors, needle holders and other instruments with a ratchet action require a lateral movement for use. For right-handers the action is natural. In the case of needle holders with a ratchet closure, the right-hander uses the right thumb to push the upper blade out and away, disengaging it. The same instrument held in a left hand requires the user to pull the top blade in an unnatural action in order to disengage it. The awkward nature of the movement can make it less fluid.
When using a pair of right hand scissors, the action is also natural and subconscious for right-handed people. With a pair of right hand scissors, the right blade is on the top, regardless of which hand you hold the instrument in. For a right hander, this offers great visibility of the cutting material. The action of a right-handed person squeezing the blades together using the index finger and the thumb causes the blades to come closer together and sheers the material being cut. This is not true for a left-handed person holding right hand scissors. First, the left-hander must look awkwardly over the scissors to view the cutting edge. Then, he or she must compensate for the unnatural action, as the right hand scissor blades tend to splay apart when squeezed with a left hand.