A device for the application of liquids, particularly high viscosity substances, such as glue and the like, comprises a layon member which is inflatable and which is connected to a filling and discharge line for causing the inflation. The device may be used to fill cracks or grooves by placing the lay-on member in the groove or crack and then inflating it. The lay-on member may also include an inner core within the envelope defining a space between the lay-on member and the core for containing the medium to be applied and which will issue from the pores of the member after the lay-on member is inflated.