A pin comprises a metal body extending along a longitudinal insertion axis (Ox) and has a first and a second end along the longitudinal axis (Ox), an upper face and a lower face opposite the upper face. The pin has two convex portions each having an inclined inner wall and an inclined outer wall, the inclined walls of each convex portion forming a ridge and extending along the longitudinal axis. At least one ridge has on its lower face a protruding blade obtained by cutting and folding the metal body along the longitudinal axis. A concave portion of the pin connects the inner walls of each convex portion via a central surface. The pin has at least one blocking member.

A connector assembly, which in one embodiment has an upper connector and in another embodiment has a lower connector. The assembly can have a gusset plate sandwiched between the upper and lower connectors. Also, disclosed is a hoistable connector assembly, a lifting frame assembly, a coupling system for modular frame units, a method for assembling a module unit using the connector assembly, and a modular frame unit and building having the connector assembly. Also, a system for coupling adjacent modular frame units for forming a modular building and a method for coupling modular frame units for forming a modular building are provided.

A method of coupling a first structure to a second structure includes providing a first bushing within an opening in an upper surface of the first structure, without the first bushing extending into a second opening in the second structure. The method further includes providing an inner opening of the first bushing which defines an inner diameter, and providing a fastener at least partially within the first bushing and at least partially within the second opening. An outer surface of the fastener defines an outer diameter. The first bushing and the fastener are configured such that a space between the outer surface of the fastener and the inner opening of the first bushing defines a gap dimensioned to increase in a direction away from the upper surface of the first structure.

A lower connector includes a lower connector hollow body, a pair of lower connector bosses coupled to the lower connector hollow body, and a pair of lower connector arms coupled to the lower connector bosses. A connector assembly includes an upper connector coupled to a lower connector and a gusset plate sandwiched between the upper and lower connectors.

A clamp bolt providing a bolt and two nut, each nut being screwed on an end of the bolt. The clamp bolt further including two washers, mounted around the bolt, and axially positioned between the two nuts.

A method of coupling a first structure to a second structure includes providing a first bushing within an opening in an upper surface of the first structure, without the first bushing extending into a second opening in the second structure. The method further includes providing an inner opening of the first bushing which defines an inner diameter, and providing a fastener at least partially within the first bushing and at least partially within the second opening. An outer surface of the fastener defines an outer diameter. The first bushing and the fastener are configured such that a space between the outer surface of the fastener and the inner opening of the first bushing defines a gap dimensioned to increase in a direction away from the upper surface of the first structure.