PURPOSE: To make a fitting of both end portions of a sheet strong and pertinent in waterproof property by winding a thermal shrinking anti-corrosive protecting sheet around a joint pipe, a coupling or the like and making it into a tube.

CONSTITUTION: Continuous protuberances 2, 2' are provided along both sides on a same surface of a thermal shrinking plastic sheet 1, 1'. Cavities 8, 8' running longitudinally along the protuberances are provided at facing surfaces 7, 7' of the protuberances 2, 2', opposing when the sheet is bended and made into a tube, at positions corresponding with each other. Sectional figures of both cavities are configurated so that widthes of portions 9, 9' nearer to the facing surfaces 7, 7' are narrower than those of portions 10, 10' remote from the surfaces. When an object to be covered is wound by this sheet, the sheet is wound so that the protuberances 2, 2' thereof are facing outwardly. The facing surfaces 7, 7' are faced so as to make a tubular hole and a long sized inserting member 12, having a thinner intermediate portion 13, is inserted into a continuous hollow portion consisting of both cavities, and thus, both terminal surfaces of the sheet may be combined.