This paper presents design details and proof-of-concept prototypes of a relative robot, so called ‘HookBot’, customized for autonomous discrete assembly of round-shape truss system elements. Initially, it examines robotic assembly systems for truss structures and highlights the similar and different features of these studies. The novel design characteristics of HookBot that differ from similar studies are the locomotion kinematics and the adhesion mechanism that improves the degree of freedom (DoF). Thus, two versions of prototype were developed, focusing on locomotion kinematics. The final version of the prototype has successfully executed the functions that enable translational, rotational, and helical locomotion on a truss strut. Besides, problems during prototyping, further improvements, successes, and failures were examined. Further, a system for truss manipulation with relative robots defines the place of HookBot within autonomous discrete assembly systems and coordinates with subsystems. Consequently, the paper discusses an autonomous system whose principal actor is relative robots and its potential contribution to future architectural services and construction systems. Also, the paper concludes that autonomous discrete assembly can be implemented with further prototypes and the examined design details.