Abstract: A fastening device for insertion into a hole in a support member has an axially straight shank having a width substantially in the range of 85-95% of the hole diameter, and an axially straight barb connected with the shank through a minor radius, such that the barb and shank can move into closely adjacent parallelism with each other when the fastener is inserted into a hole and the barb is in a flexed and stressed condition, the barb having a length in the range of 90-140% of the hole diameter, and, in its unstressed condition, subtending an acute angle of 30.degree.-45.degree. with respect to the shank.