PROBLEM TO BE SOLVED: To improve the finish of a built-up coffin by reducing portions having a visible joint or seam between plates in the appearance after the assembly, facilitate the fabrication of joints between fold-down side plates and inserted end plates (engaging grooves and engaging protrusions), and maintain a satisfactory strength of the joints.SOLUTION: A coffin 10 includes a bottom plate 12A connected with basal side plates 12B on the left and right long sides, and basal end plates 12C on the front and rear short sides. Fold-down side plates 12X are disposed above the basal side plates 12B. Inserted end plates 12Y are jointed to the front and rear external surfaces of the plates 12C, 12B, and 12X. The basal side plates 12B and the fold-down side plates 12X are respectively provided with lower engaging protrusions 17 and upper engaging protrusions 18 on the front and rear end faces. The inserted end plates 12Y include engaging grooves 16 (FIG. 6), into which the protrusions 18 and 17 can be slid, along the lateral edges of the internal surfaces of the inserted end plates 12Y. Gaps 19a reside above the upper engaging protrusions 18, while covering portions 19b (FIG. 6), which fit in the gaps 19a, reside above the engaging grooves 16.COPYRIGHT: (C)2014,JPO&INPIT【課題】組み立て後の外観に板材の継ぎ目や切れ目が見える箇所を少なくして仕上がりを良好にした上で、可倒側板と差込妻板との継ぎ目(係合溝と係合突起)の製造を容易にし、継ぎ目の強度を良好に保つ。【解決手段】棺桶10は、底板12Aの左右長辺側に基礎側板12B、前後短辺側に基礎妻板12Cを有する。基礎側板12Bの上側に可倒側板12Xが設けられ、これらの板12C、12Bおよび12Xの前後外側に差込妻板12Yが継ぎ合わされる。基礎側板12Bおよび可倒側板12Xの前後の端面には、下部係合突起17および上部係合突起18が設けられる。差込妻板12Yの内側面の側端部には、これらの突起18,17にスライド挿入可能な係合溝16(図6)が設けられる。上部係合突起18の上方には空隙部19a、係合溝16の上方には空隙部19aに収まる被せ部19b(図6)が設けられる。【選択図】図2