Female Snap Button and Snap Button

A female snap button with which a post of a male snap button is engageable and disengageable, the female snap button comprising:

• a first member at least partially-defining an aperture to which the post is inserted, the aperture being capable of expanding in accordance with the insertion of the post and capable of recovering from the expanded aperture width to its initial aperture width;
• and
• a second member capable of restricting the expansion of the aperture so as to increase the force required to engage and disengage the post for the female snap button or so as to prohibit it from engaging and disengaging therewith;
• wherein the second member comprises at least one contact portion that is to be in contact with the first member, and the first member comprises at least one contacted portion that is to be contacted with the contact portion,
• and wherein the extent of the expansion of the aperture allowed by the second member varies in accordance with the relative position of the contact portion and the contacted portion in the circumferential direction that is around the insertion direction of the post into the aperture.