28 which open neck portion 21 may have any desirable dimensions including but not limited to an extremely narrow slot it is also preferable that the origin sections 28 are substantially perpendicular to the head 12 as they initiate from the lower side 16 of the head 12 and then lean toward each other at a later point as they progress to reach the respective front portions 26 each origin section 26 has an inner surface s 1 and an outer surface s 2 which outer surface s 2 may preferably have anti sliding elements 32 examples of such anti sliding elements 32 are ripples bent teeth general roughness bumps and any other configuration which will resist extraction of the fastener 10 from a slot 34 of a substrate or first object 36 see fig4 when said fastener 10 is pulled away from the slot 34 especially after insertion of the expanding member 20 see fig6 substrates or first objects are usually panels such as metal sheets for example having a thickness t and slots 34 with a width w see fig4 the slot 34 has preferably an oblong shape with a round hole in the middle as better illustrated in fig4 a the round hole allows the expanding member to move through the slot freely without interference from the walls of the slot especially if the substrate or first object 36 is too thick and or too hard examples of anti sliding configurations and more details regarding their structure as well as other types of spring fasteners having snapping segments are disclosed in.