There are several options:
- using a printout of the certificate on paper
- using the Tečka app
- using the certificate in electronic form, downloaded from the Vaccination Portal (uzis.cz)
- using an image of the QR code from the certificate, stored on your device
The most simple option is using the čTečka and Tečka apps. The čTečka app can detect whether a QR code from a certificate (regardless of whether downloaded into the Tečka app or, for instance, as part of a printed out certificate) is indeed genuine and not forged. Detailed instructions on how to use the apps can be found at ockodoc.cz.
If you are unable to download your certificate (most frequent reasons are errors when entering your data - a typo in your name, ignoring case sensitivity, entering another of your multiple e-mail addresses, bad punctuation, etc.), you can contact the 1221 hotline. You can spare your time by checking if the data the vaccination point personnel enters to the ISIN are correct and memorizing them.