more doc updates

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diff --git a/docs/reference/src/SUMMARY.md b/docs/reference/src/SUMMARY.md
index c605fa3b..ce473546 100644
--- a/docs/reference/src/SUMMARY.md
+++ b/docs/reference/src/SUMMARY.md
@@ -9,6 +9,7 @@
 - [Protocols](./protocols/index.md)
 
   - [BUS](protocols/bus.md)
+  - [REP](protocols/rep.md)
 
 - [Transports](./transports/index.md)
 
@@ -53,6 +54,7 @@
     - [nng_cv_wait](api/nng_cv_wait.md)
     - [nng_cv_wake](api/nng_cv_wake.md)
     - [nng_cv_wake1](api/nng_cv_wake1.md)
+    - [nng_free](api/nng_free.md)
 
   - [Context Functions](api/context.md)
 
diff --git a/docs/reference/src/api/nng_free.md b/docs/reference/src/api/nng_free.md
new file mode 100644
index 00000000..cc1d3308
--- /dev/null
+++ b/docs/reference/src/api/nng_free.md
@@ -0,0 +1,35 @@
+# nng_free()
+
+## NAME
+
+nng_free --- free memory
+
+## SYNOPSIS
+
+```c
+#include <nng/nng.h>
+
+void nng_free(void *ptr, size_t size);
+```
+
+## DESCRIPTION
+
+The `nng_free()` function deallocates a memory region of size _size_,
+that was previously allocated by [`nng_alloc()`](nng_alloc.md) or
+[`nng_recv()`](nng_recv.md) with the `NNG_FLAG_ALLOC` flag.
+
+> [!IMPORTANT]
+> It is very important that _size_ match the allocation size
+> used to allocate the memory.
+
+> [!IMPORTANT]
+> Do not attempt to use this function to deallocate memory
+> obtained by a call to the system `malloc()` or `calloc()` functions,
+> or the C++ `new` operator.
+> Doing so may result in unpredictable
+> behavior, including corruption of application memory.
+
+## SEE ALSO
+
+[nng_alloc()](nng_alloc.md),
+[nng_recv()](nng_free.md)
diff --git a/docs/reference/src/protocols/rep.md b/docs/reference/src/protocols/rep.md
new file mode 100644
index 00000000..cb602e47
--- /dev/null
+++ b/docs/reference/src/protocols/rep.md
@@ -0,0 +1,56 @@
+# REP Protocol
+
+{{hi:protocol, _REP_}}
+The {{i:_REP_ protocol}} is one half of a {{i:request/reply pattern}}.
+In this pattern, a requester sends a message to one replier, who
+is expected to reply.
+The request is resent if no reply arrives,
+until a reply is received or the request times out.
+
+> [!TIP]
+> This protocol is useful in setting up RPC-like services.
+> It is also reliable, in that a requester will keep retrying until
+> a reply is received.
+
+The _REP_ protocol is the replier side, and the
+[_REP_](req.md) protocol is the requester side.
+
+## Socket Operations
+
+The [`nng_rep0_open()`](nng_rep_open.md) functions create a replier socket.
+This socket may be used to receive messages (requests), and then to send
+replies.
+
+Generally a reply can only be sent after receiving a request.
+
+Send operations will result in `NNG_ESTATE` if no corresponding request
+was previously received.
+
+Likewise, only one receive operation may be pending at a time.
+Any additional concurrent receive operations will result in `NNG_ESTATE`.
+
+[Raw](../overview/raw.md) mode sockets ignore all these restrictions.
+
+## Context Operations
+
+This protocol supports the creation of [contexts](../api/nng_ctx.md) for concurrent use cases using [`nng_ctx_open()`](../api/nng_ctx_open.md).
+
+Each context may have at most one outstanding request, and operates
+independently of the others.
+The restrictions for order of operations with sockets apply equally
+well for contexts, except that each context will be treated as if it were
+a separate socket.
+
+## Protocol Versions
+
+Only version 0 of this protocol is supported.
+(At the time of writing, no other versions of this protocol have been defined.)
+
+## Protocol Options
+
+The _REP_ protocol has no protocol-specific options.
+
+## Protocol Headers
+
+The _REP_ protocol uses a {{ii:backtrace}} in the header.
+This is more fully documented in the [_REQ_](req.md) chapter.