  The axion haloscope is the currently most sensitive method to probe the
vanishingly small coupling of this prominent Dark Matter candidate to photons.
To scan a sizeable axion Dark Matter parameter space, the cavities that make up
the haloscope need to be tuned efficiently. In this article, we describe a
novel technique to tune axion haloscopes around $8.4$ GHz in a purely
mechanical manner without the use of dielectrics. We achieve tuning by
introducing a gap along the cavity geometry. Losses are added due to the
leaking of the field out of the structure only if the gap becomes too large
concerning the total width. A tuning range of around $600$ MHz is achieved,
depending on the environmental conditions. We present the results of a
corresponding prototype and outline prospects to further develop this
technique.
