Abstract: A trowel suitable for spreading underlayment onto a floor and for later spreading an adhesive layer over the hardened underlayment. It makes use of a rail on one side of which the handle is mounted and on the other side of which the blade is mounted. The blade is of a spring metal, and the rail is in the form of a U-shaped channel member secured to the central portion of the blade. The rail is wider than the handle, and covers about 87% of the length and about 60% of the width of the blade, to stiffen the blade while leaving its edges somewhat flexible. The rail is also provided with flange on each side of the channel portion, and the flanges each contain openings for receiving spring clips bent up from the blade, so that the blade can be easily mounted to and demounted from the rail. Punched-up detents on the blade cooperate with bent-down ends of the channel to hold the blade in position on the rail while permitting its easy release for cleaning or replacement.