Straight guide wires can be modified into both simple and complex curves in a matter of seconds using only the thumb and forefinger. The guide wire is held between the thumbnail and the index finger (fig. i ). By squeezing the thumbnail against the index finger and pulling the wire through, a curve will be formed in the wine concave toward the thumbnail. Increasing the pressure between the thumbnail and the forefinger will yield a tighter curve in the guide wire. The length of the curve is determined by the length of wire pulled between the thumbnail and forefinger. Besides a thumbnail, any tightly curved surface such as the edge of a Kelley clamp may be used; however, tactile control is lost and wire damage is more likely to occur. Two types of wire damage may occur. One is an acute bend or kink, which is easily visible; the other is helix separation, which can be identified by attempting to stretch gently the newly formed part of the wire. Wine lengthening and separation of the adjacent coils will be present with helix separation. Excessive force will lead to helix separation in an undamaged wire. Either type of damage may result in an inability to remove the wine from the catheter. If this happens, the wine and catheter must be removed as a unit or through a sheath. Wires with bong flexible ends and bong tapered cores, such as TSFNB Newton LLT, TSFHA-B-D Hilal Grossman, and TSUF and TSFB Bentson, will have a tighter radius of curvature for a given pressure than wines with short tapers and heavier cores, such as TSF, THSF, on TSFNA Newton LT (these names and abbreviations refer to wires made by Cook; many companies make analogous wires that can be curved just as readily). Difficulty may be encountered in placing the curved wine into the catheter. This is especially true with tight curves on flexible tips. For simple, open J-type curves, the maneuver of pushing the thumb forward toward the tip of the wine while sweeping the index and remaining fingers away from the tip often will straighten the curves sufficiently to advance the wire into the catheter. For tight and complex curves, it is preferable to use an introducer of some kind. Once a curve has been placed on a wine, it often can be restraightened by curving the wine in the opposite direction. This is done by applying thumbnail force along the convex surface of the curve. This maneuver does not always yield a perfectly straight result and may cause separation of the outer wire helix. One should check for helix separation after any curvature modification.