Anatomy of the Human Hand: A Mini Guide for Hand Tool Users

The hand makes both powerful and precise movements possible through the harmonious operation of bones, muscle-tendons, nerves and sensors (receptors that detect touch) at the fingertips. The following brief tour summarises the basic biomechanics behind the control you feel in everyday life by adding scientific terms alongside simple explanations.

1) Skeleton: 27 parts "carrier" architecture
A hand has eight carpal (wrist bones), five metacarpals (palm bones) and 14 phalanges (finger bones). This structure transfers force from the wrist to the tips of the fingers efficiently while allowing agile movements.

2) Muscle-tendon duo: Power work and fine work
The muscles of the hand are considered in two groups: extrinsic muscles (muscles starting in the forearm, whose tendon extends to the hand and produce more than a "large force") and intrinsic muscles (originating from the hand, fine-tuning and positioning of the fingers and small muscles). This division of labour enables both the generation of power when cutting thick cardboard and power production, as well as precision when managing millimetre curves in a model.

3) "Reel" system: A2 and A4's critical role
On the inner face of the finger flexor tendons (rope-like structures that serve to flex the fingers and transmit muscle power to the fingers), pass through annular pulleys (ring-shaped ligament bands) called tunnels. In particular, A2 and A4 pulleys (the two most important pulley bands) hold the tendon close to the bone, reducing the risk of bowstringing (spring beam-like popping out); thus, minimising the loss of power in grip.

4) Thumb magic: Opposing resisting (opposition)
The CMC joint (trapeziometacarpal; the main multi-directional joint of the thumb) at the base of the thumb enables opposition (the thumb opposing the other fingers) to occur. This movement provides a large part of the precise grip and secure grip.

5) Grip types: Power or precision?
The classic classification distinguishes two basic strategies: power grip (high-force grip, where the fingers press the palm) and precision grip (grip where the thumb-index/middle finger triad adjusts the position with small forces). In everyday work, these two strategies become fluidly intertwined.

6) Finger tip "sensors":
Mechanoreceptors (sensors for touch and mechanical stimulation) in the skin, Meissner bodies (slight contact and sliding on the surface), Merkel cells (constant pressure and edge differentiation), Pacini bodies (high frequency vibration) and Ruffini end organs (skin stretching and shape change). This network enables instantaneous adjustment of the gripping force; it helps to run the blade over the line without pressing more than necessary.

7) Friction, moisture and "wrinkled finger" effect
Skin hydration (skin moisturisation level) modifies finger-surface friction and the slip threshold. Finger wrinkling (temporary wrinkling of the skin surface ), seen after exposure to water, can reduce the grip force required when holding wet objects; i.e. increase efficiency.

8) Nerve network: Median-Ulnar-Radial triad
Sensory and motor control of the hand; median nerve ( sensitive movement and sensation around the thumb-index and index finger ). It is provided by the ulnar nerve (the line that runs most of the intrinsic muscles on the side of the little finger ) and by the radial nerve (especially the hand dorsal sensory and finger extensor muscles). This "wiring" coordinates the power-sensitivity balance.

Ergonomics Tip Boxes

• Precise cutting: Holding your wrist straight and bringing the blade close to the surface at an angle of about 10-20° to the surface can create smoother lines in one pass without going deeper in several slight passes.
• Long line: The use of a metal ruler and preferably a non-slip base increases line continuity; fixing the ruler to the side of the body reduces unwanted escapes.
• Grip confidence: Dry/sweaty hands, or gloves with TPE-coated bodies (e.g., MUK09 / VMUK09) can reduce slippage by increasing friction.
• Blade maintenance: Snap at the blunted segment at the tips safely breaks; at the trapezoidal tips, if blunted, immediately replace them to improve the quality of cut and safety.

UTTIL & Connection with Mozart: Reflection of Science into Product

• Grip and friction: NMUK09 / The HIPS body TPE + sheath on the VMUK09 supports control (pen/pinch) and power grip.
• Choice of mechanism: NMUK (automatic lock) for fast use in smooth work; VMUK (screw clamping) for long lines for those who want to adjust the blade stability manually.
• Blade character (pocket types): PTUK07 (9 mm) and PTUK08 (18 mm) families standard, 30° precision, segmentless and TiN-coated variants make it easy to choose the power-precise balance that the job requires.
• Trapezoidal applications: PAUK06 (3-stage blade output) and PRUK06 (automatic retraction) with "trigger-like" grips offer rhythmic and safe advancement in warehouse/packaging processes.
• Sharpness standard: Mozart Blades (Solingen); 9 mm/18 mm snap-off, 30° precision, TiN coated, segmentless and trapezoidal/hook blade options produce clean and repeatable cuts.

 Quick Selection Table

Short Security Summary

• It is generally safer to make cuts away from the body.
• Turning off the blade or locking it, or when the work is finished, reduces the possibility of accidents.
• Keeping the working surface flat, dry and non-slip increases the feeling of control.
• It is recommended to accumulate the snap-off segments in a safe container and replace them immediately when the trapezoidal tips become blunt.
• When using the PRUK06, seeing the blade automatically retract at the end of the cut provides an added level of safety.

Scientific Sources (Openly)

1.    Standring S. Grey's Anatomy: The Anatomical Basis of Clinical Practice. 42nd Edition. Elsevier; 2020. (basic reference for bones and joints of the hand).

2.     Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. 8th Edition. Wolters Kluwer; 2018. (Anatomy of the upper extremity and hand).

3.     Orthobullets. Flexor Pulley System - Hand. (Clinical and biomechanical importance of A2-A4 pulley structures and the bowstringing concept.)

4.     Bosco F. Closed flexor pulley injuries: a literature review. Orthopaedic Reviews. 2022;14(1).(Pulley injuries and function.)

5.     Napier JR. The prehensile movements of the human hand. J Bone Joint Surg Br. 1956;38-B(4):902-91313. (The classic source of the power-sensitive grip classification.)

6.     Abraira VE, Ginty DD. The sensory neurons of touch. Neuron. 2013;79(4):618-639. (Mechanoreceptor Types and Physiology of Touch)

7.     Kareklas K, Nettle D, Smulders T. Water-immersion finger-wrinkling improves handling of wet objects. PLOS ONE. 2013. (Wrinkled fingers and grip efficiency.)