Figure 1.

Penetrating needle for double blinding with outer guide tube. (A) Outer guide tube; (B) Before tapping-in method. The upper part of the needle handle protrudes from the outer guide tube by 4 mm. The inner diameter of the upper part of the outer guide tube from the top of the inner tube is slightly larger than the diameter of the needle handle, and the inner diameter of the rest of the lower part of the outer guide tube is slightly larger than the outer diameter of the inner opaque tube, which stabilizes the needle handle in the outer guide tube during the tapping-in method application; (C) After tapping-in method. The protruding part (4 mm) of the needle handle is inserted into the outer guide tube using the tapping-in method to penetrate the skin. (For the skin-touch and the no-touch placebo needle, needle tips penetrate the lower stuff in the inner tube at this stage.); (D) Needle insertion after removal of the outer guide tube. After the tapping-in method, the outer guide tube is removed, and the needle is inserted using the alternating twirling technique. The inner diameter of the inner tube is smaller than the diameter of the needle handle so that the inner tube works as a stopper. (The blunt tip of the skin-touch needle slightly protrudes from the inner tube to touch the skin but not for the no-touch placebo needle at this stage).