How to check DC offset without any tools

What tools do I use? https://youtu.be/MLK649c1_fM This is a fun little DIY something I noticed playing around with vintage stereos over the years. Technically, you could fully adjust the DC offset without a multimeter, but I would not necessarily recommend that. This video is just for CHECKING, not setting. This applies to any receiver or amplifier with adjustable DC offset. Marantz, Pioneer, Sansui, Kenwood, and many other stereo brands made models that have adjustable DC offset, so this applies to any of those. Thanks for watching!