Toy block

A toy block comprising:

• a base section configured such that, taking a unit edge length to be 1 and a cube expressed as 1×1×1 to be one unit size, comprises a parallelepiped shape of size approximately equal to one or more conjoined unit sizes, four lateral walls, a roof and a bottom comprising a hollow face;
• and
• a cylindrical projection of a cylindrical shape provided on at least one of the roof and the lateral walls, with a diameter being equal to or greater than 0.45 but less than 0.55 with respect to the unit edge length, and a height being (1−diameter)×(0.45 to 0.5 inclusive);
• wherein the base section comprises an interlocking section enclosed by the four lateral walls, the interlocking section configured to contact and interlock with at least one cylindrical projection of another toy block with an identical shape to the cylindrical shape;
• and
• a wall thickness near the bottom expressed as
• (1−diameter)×0.5+alpha, where
• alpha is between −0.05 and 0.03 inclusive, and
• wherein the parallelepiped shape comprises a size of at least 2×2 or more conjoined unit sizes, and the interlocking section comprises a middle partition not connected to the lateral walls comprising an outside face comprising a long wall comprising a depression configured to contact with the at least one cylindrical projection of another toy block at the depression and at least one of the lateral walls facing the middle partition;
• and
• wherein the depression comprises a trapezoidal shape with legs having a gentler slope than a curvature of the cylindrical shape so that the depression is configured to contact the at least one cylindrical projection at a line of maximal depression.