diff --git a/parquet/src/record/record_reader.rs b/parquet/src/record/record_reader.rs
index 938c14b29406..34d93262b016 100644
--- a/parquet/src/record/record_reader.rs
+++ b/parquet/src/record/record_reader.rs
@@ -19,6 +19,8 @@ use super::super::errors::ParquetError;
 use super::super::file::reader::RowGroupReader;
 
 /// read up to `max_records` records from `row_group_reader` into `self`
+/// The type parameter `T` is used to work around the rust orphan rule
+/// when implementing on types such as `Vec<T>`.
 pub trait RecordReader<T> {
     fn read_from_row_group(
         &mut self,
diff --git a/parquet/src/record/record_writer.rs b/parquet/src/record/record_writer.rs
index 5a749dec407a..a9cbbbe6ccec 100644
--- a/parquet/src/record/record_writer.rs
+++ b/parquet/src/record/record_writer.rs
@@ -22,6 +22,8 @@ use super::super::file::writer::SerializedRowGroupWriter;
 
 /// `write_to_row_group` writes from `self` into `row_group_writer`
 /// `schema` builds the schema used by `row_group_writer`
+/// The type parameter `T` is used to work around the rust orphan rule
+/// when implementing on types such as `Vec<T>`.
 pub trait RecordWriter<T> {
     fn write_to_row_group<W: std::io::Write + Send>(
         &self,