diff --git a/README.md b/README.md
index 56d865dd..548ebfe9 100644
--- a/README.md
+++ b/README.md
@@ -408,6 +408,13 @@ you may refer to the man pages of the applications, respectively.
                                   (not available in redir mode)
 
        [-b <local_address>]       Local address to bind.
+                                  For servers: Specify the local address to use 
+                                  while this server is making outbound 
+                                  connections to remote servers on behalf of the
+                                  clients.
+                                  For clients: Specify the local address to use 
+                                  while this client is making outbound 
+                                  connections to the server.
 
        [-u]                       Enable UDP relay.
                                   (TPROXY is required in redir mode)
diff --git a/doc/shadowsocks-libev.asciidoc b/doc/shadowsocks-libev.asciidoc
index d6d4c530..f97aeb9f 100644
--- a/doc/shadowsocks-libev.asciidoc
+++ b/doc/shadowsocks-libev.asciidoc
@@ -101,9 +101,15 @@ multi-interface environment.
 Not available in redir mode.
 
 -b <local_address>::
-Specify local address to bind.
+Specify the local address to bind.
 +
-Not available in server nor manager mode.
+For servers: Specify the local address to use while this server is making 
+outbound connections to remote servers on behalf of the clients.
++
+For clients: Specify the local address to use while this client is making 
+outbound connections to the server.
++
+Not available in manager mode.
 
 -u::
 Enable UDP relay.
diff --git a/doc/ss-local.asciidoc b/doc/ss-local.asciidoc
index 0c7cbfde..68fc8354 100644
--- a/doc/ss-local.asciidoc
+++ b/doc/ss-local.asciidoc
@@ -93,7 +93,8 @@ That results the traffic go out through eth1, but not lo nor eth0.
 This option is useful to control traffic in multi-interface environment.
 
 -b <local_address>::
-Specify local address to bind.
+Specify the local address to use while this client is making outbound 
+connections to the server.
 
 -u::
 Enable UDP relay.
diff --git a/doc/ss-redir.asciidoc b/doc/ss-redir.asciidoc
index c03f0236..f8008b5f 100644
--- a/doc/ss-redir.asciidoc
+++ b/doc/ss-redir.asciidoc
@@ -83,7 +83,8 @@ Specify max number of open files.
 Only available on Linux.
 
 -b <local_address>::
-Specify local address to bind.
+Specify the local address to use while this client is making outbound 
+connections to the server.
 
 -u::
 Enable UDP relay.
diff --git a/doc/ss-server.asciidoc b/doc/ss-server.asciidoc
index 3ac3d196..0dcddffa 100644
--- a/doc/ss-server.asciidoc
+++ b/doc/ss-server.asciidoc
@@ -88,7 +88,8 @@ That results the traffic go out through eth1, but not lo nor eth0.
 This option is useful to control traffic in multi-interface environment.
 
 -b <local_address>::
-Specify local address to bind.
+Specify the local address to use while this server is making outbound 
+connections to remote servers on behalf of the clients.
 
 -u::
 Enable UDP relay.
diff --git a/doc/ss-tunnel.asciidoc b/doc/ss-tunnel.asciidoc
index 1e0e4fff..a6f212a9 100644
--- a/doc/ss-tunnel.asciidoc
+++ b/doc/ss-tunnel.asciidoc
@@ -92,7 +92,8 @@ That results the traffic go out through eth1, but not lo nor eth0.
 This option is useful to control traffic in multi-interface environment.
 
 -b <local_address>::
-Specify local address to bind.
+Specify the local address to use while this client is making outbound 
+connections to the server.
 
 -u::
 Enable UDP relay.