diff --git a/README.md b/README.md
index d673048..ee71b2b 100644
--- a/README.md
+++ b/README.md
@@ -94,3 +94,16 @@ Build
 ```shell
 fedpkg build --target=f34-build-side-12345
 ```
+
+## RHEL/CentOS builds
+
+RHEL and CentOS use a different approach for Rust crates packaging than
+Fedora. On Fedora Rust dependencies are packaged as RPMs, e.g.
+``rust-pyo3+default-devel`` RPM. These packages don't exist on RHEL and
+CentOS. Instead python-cryptography uses a tar ball with vendored crates.
+The tar ball is created by a script:
+
+```shell
+./vendor_rust.py
+rhpkg upload cryptography-3.4-vendor.tar.bz2
+```