We are interested in the interaction between electromagnetic (EM) waves and a material composed of two interwoven metallic networks. At low frequencies, these materials give rise to electron acoustic waves, in which the electric field oscillates longitudinally to the propagation direction. These carry quasi-bound states in the continuum (quasi-BICs) for a slab-terminated material, resonances with extremely long lifetimes. The quasi-BICs can be excited depending on the slab termination and inclination and the EM waves' incident angle. We here aim to understand this relationship through modelling and microwave experiments.