A support device includes a linkage rod movable along a first direction and a contact indication structure including an abutting shell, a pushing member, an indication member and a transmission member. The pushing member is movable and has a first position and a second position. The indication member having a first indication information is movable. The pushing member and the indication member are located at two sides of the linkage rod in a second direction. The transmission member is movable and extends between the pushing member and the indication member. When the pushing member is in the first position, the first indication information is hidden within the abutting shell; and when the pushing member is in the second position, the first indication information is exposed from the abutting shell. The pushing member is movable towards the second position to drive the indication member and the transmission member to move.

A seat (1000) may include mounting components (1054a, 1054b) that may mate with corresponding components on other assemblies. The seat may include one or more features that may rotate or move to provide for coupling to the one or more assemblies. Assemblies include, but are not limited to, a stroller, a bicycle adapter, a wagon, a booster seat, a camping chair, a high chair, a stadium seat/picnic table, a hiking pack, an infant carrier, a car seat, a booster car seat, or an airline seat.