The investigators developed a bench-top knot tying simulator (KNOTI), with computer acquired assessment. Fifteen attending surgeons and 30 first year surgical residents were recruited to the study held at tertiary medical center during the years 2017-2018. The participants tied eight knots in different settings (Superficial vs. Deep) and techniques (One hand vs. two hands).

The simulator is a bench-top simulator with computer acquired assessments, designed to allow novices to acquire basic surgical skills in knot tying. The simulator measures the forces used and applied on the tissue while ligating a vessel.

Each participant received instructions for approximately 10 minutes with a standardized and detailed explanation of the knot-tying technique. All knots were square knots (double-throw knot) using the same type of sutures (SOLFSILK 3.0). Participants were asked to tie two knots in four types: A superficial one hand square knot; A superficial two hand square knot; A deep one hand square knot; A deep two hand square knot.

For each knot six parameters were extracted from the sensor data: maximum upward force, maximum downward force, total upward force, total downward force, absolute non-zero force and performance time. Maximum force is the highest force applied during the knot tying.

Participants were not aware of what exact parameters the simulator was assessing. Novices were explained to avoid tissue rupture or loose knots. Knot integrity was evaluated by an investigator present during the simulation that discarded "air knots". Videos were reviewed by an investigator at post-study analysis to verify the appropriate technique and knot integrity.

Inclusion Criteria:

• residents within their first year of surgical residency
• attending physicians from general surgery, vascular surgery, cardio-thoracic surgery and gynecology services.

Exclusion Criteria:

-