A method for performing a task in a tight place in an elongated profile, preferably in a wing blade with an outer shell for a wind power plant, whereby at least one barrier is formed transversely of at least one elongated channel in the profile and a balloon for use in performing the task. The method may include the following steps: establishing a number of inspection and mounting holes in the surface of the shell, mounting at least one inflatable balloons in the at least one channel, filling the balloon(s) with air, and applying at least one first material layer between the sidewalls of the elongated channel and across the balloon(s), the layer preferably being expanding polyurethane foam. The applied layer of material fills cracks and gaps between balloons and wing parts, providing a load-bearing layer between these parts. An additional layer may subsequently be laid upon the former layer.