Intelligent reflecting surface (IRS) has emerged as a promising solution to enhance communication performance via passive signal reflection. In this paper, we propose a dual distributed-IRS aided communication system, where two IRSs are deployed in a distributed manner to extend the communication coverage of an access point (AP) to a target area. Specifically, we aim to maximize the worst-case signal-to-noise ratio (SNR) over all locations in the target area by jointly optimizing the passive beamforming and deployment for the two distributed IRSs. To solve this problem, we propose an efficient two-step algorithm by first designing the IRSs' passive beamforming optimization given IRSs' locations and then optimizing the IRS deployment. Our simulation results show that given the same total number of reflecting elements, deploying two distributed IRSs can achieve much better coverage performance than deploying one centralized IRS.