Abstract: A portable holding clamp for applying patches for the repair of tire sidewalls comprises a rigid beam member adjustable telescopically to accommodate tires having various chord widths, integrally attached rim coupling means, manually actuated patch pressurizing means located midway of the beam and a quick attaching and holding means for attaching the clamp to a track or tread belt of the tire. The quick attaching and holding means includes a key-shaped slot formed on the beam, opposite the rim coupling means, for facilitating rapid adjustment of a holding chain on which either a key-shaped latching member or a barbed latching member is used for quick attachment to the tire, depending on whether the tire has a track belt or tread belt mounted therearound. Thus, the clamp can be quickly and conveniently positioned to effect tire sidewall patch repairs. A method of repairing such tire sidewalls is also disclosed herein.