Simple engaging device

A simple engaging device in furniture with two flat pieces comprising:

• a locating base being embedded in one of the two flat pieces, and further comprising a facial base section and a rear base section which are integrated as one piece, at least a longitudinal hole with two circular ends, and one of the circular ends being an enlarged circular end;
• at least a locating stem being embedded to another one of the two flat pieces corresponding to the locating base, and having an engaging head and a joining part with a reduced diameter extending outward to be inserted into the longitudinal hole via the enlarged circular end;
• wherein the facial base section has two ends and the rear base section has two ends as well, the facial base section is longer than the rear base section, and a distance between one of the two ends of the facial base section and one of the two ends of the rear base section near the end of the facial base section being different from and a distance between the other end of facial base section and the other end of the rear base section to offer a function of foolproof so as to avoid assembling mistakes;
• there are two identical flat locating parts oppositely disposed at two long sides of each longitudinal hole;
• each of the flat locating parts has a slant plane next to the enlarged circular end, a first slender retaining projection disposed near the slant plane to extend across the respective locating part, a step disposed next to the first thin retaining projection and extending to the other circular end of the respective longitudinal hole, and a second slender retaining projection disposed near the other circular end of the respective longitudinal hole extending across the respective locating part to the step;
• the slant plane makes the engaging head and the joining part easy to be assembled and is capable of tightly guiding the engaging head and the joining part to reach the first retaining projection which is capable of securing the engaging head and the joining part firmly without loosening, and the step and the second thin retaining projection are capable of engaging the engaging head and the joining part to the locating parts in case of the engaging head and the joining part being worn out.