As principals focus on instructional leadership, principal supervisors must shift from the managerial stance to developing principals' instructional leadership capacity. The problem is supervisors are unprepared to support principals in shifting to instructional leadership, due to a lack of time and instructional leadership capacity to engage in evaluative and coaching relationships centered on a culture of trust, given the lack of clarity on effective walkthrough design. A gap in the literature exists on effective coaching and evaluation of principals, but trust must exist in the relationship. The purpose of this basic qualitative study was to explore how trust in the evaluative and coaching relationship between the principal and supervisor is affected by walkthrough design. Management by Wandering Around and ABCDTrust comprise the theoretical framework. Fifteen principals experienced in walkthroughs for evaluation were recruited via social media to engage in semi-structured interviews. Three research questions guided the study: principals described the ideal walkthrough, shared perceptions of the walkthrough as part of personal evaluation and professional development (PD), and described how trust manifested through walkthrough design, including observation group composition, duration, and type and style of feedback. Interviews were coded and analyzed using thematic analysis. Key results indicated that principals desired formative walkthroughs with more regular check-ins and authentic conversations about instructional practices. Design of the walkthroughs impacted principals' trust in the supervisor. Recommendations include increasing aspects of formative supervision and co-constructing walkthrough protocols and feedback. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]