diff --git a/README.md b/README.md
index 778d58f2..c292801a 100644
--- a/README.md
+++ b/README.md
@@ -20,6 +20,7 @@
   * [The header](#the-header)
   * [The *preflight* section](#the-preflight-section)
     * [Supported *preflight* options](#supported-preflight-options)
+    * [More about *pcb_replace* and *sch_replace*](#more-about-pcb_replace-and-sch_replace)
     * [Filtering DRC and ERC errors](#filtering-drc-and-erc-errors)
   * [Default global options](#default-global-options)
     * [Default *output* option](#default-output-option)
@@ -118,6 +119,7 @@ This section is used to specify tasks that will be executed before generating an
     - *regexp*: Alias for regex.
 - `ignore_unconnected`: [boolean=false] Option for `run_drc`. Ignores the unconnected nets. Useful if you didn't finish the routing.
 - `pcb_replace`: [dict] Replaces tags in the schematic. I.e. to insert the git hash or last revision date.
+        This pre-flight modifies the PCB. Even when a back-up is done use it carefully.
   * Valid keys:
     - `date_command`: [string=''] Command to get the date to use in the PCB.\
                       ```git log -1 --format='%as' -- $KIBOT_PCB_NAME```\
@@ -139,6 +141,7 @@ This section is used to specify tasks that will be executed before generating an
 - `run_erc`: [boolean=false] Runs the ERC (Electrical Rules Check). To ensure the schematic is electrically correct.
         The report file name is controlled by the global output pattern (%i=erc %x=txt).
 - `sch_replace`: [dict] Replaces tags in the schematic. I.e. to insert the git hash or last revision date.
+        This pre-flight modifies the schematics. Even when a back-up is done use it carefully.
   * Valid keys:
     - `date_command`: [string=''] Command to get the date to use in the SCH.\
                       ```git log -1 --format='%as' -- $KIBOT_SCH_NAME```\
@@ -172,6 +175,15 @@ preflight:
   ignore_unconnected: false
 ```
 
+#### More about *pcb_replace* and *sch_replace*
+
+These options are supposed to be used in a version control environment.
+This is because, unlike other options, they modify the PCB and/or schematic and might damage them.
+In a version control environment you can just roll-back the changes.
+
+Don't be afraid, they make a back-up of the files and also tries to disable dangerous changes.
+But should be used carefully. They are ideal for CI/CD environment where you don't actually commit any changes.
+
 #### Filtering DRC and ERC errors
 
 Sometimes KiCad reports DRC or ERC errors that you can't get rid off.
diff --git a/docs/README.in b/docs/README.in
index fa51f04e..3e7ebf32 100644
--- a/docs/README.in
+++ b/docs/README.in
@@ -20,6 +20,7 @@
   * [The header](#the-header)
   * [The *preflight* section](#the-preflight-section)
     * [Supported *preflight* options](#supported-preflight-options)
+    * [More about *pcb_replace* and *sch_replace*](#more-about-pcb_replace-and-sch_replace)
     * [Filtering DRC and ERC errors](#filtering-drc-and-erc-errors)
   * [Default global options](#default-global-options)
     * [Default *output* option](#default-output-option)
@@ -116,6 +117,15 @@ preflight:
   ignore_unconnected: false
 ```
 
+#### More about *pcb_replace* and *sch_replace*
+
+These options are supposed to be used in a version control environment.
+This is because, unlike other options, they modify the PCB and/or schematic and might damage them.
+In a version control environment you can just roll-back the changes.
+
+Don't be afraid, they make a back-up of the files and also tries to disable dangerous changes.
+But should be used carefully. They are ideal for CI/CD environment where you don't actually commit any changes.
+
 #### Filtering DRC and ERC errors
 
 Sometimes KiCad reports DRC or ERC errors that you can't get rid off.
diff --git a/docs/samples/generic_plot.kibot.yaml b/docs/samples/generic_plot.kibot.yaml
index 6b6e9a0c..8a434134 100644
--- a/docs/samples/generic_plot.kibot.yaml
+++ b/docs/samples/generic_plot.kibot.yaml
@@ -18,6 +18,7 @@ preflight:
   # [boolean=false] Option for `run_drc`. Ignores the unconnected nets. Useful if you didn't finish the routing.
   ignore_unconnected: false
   # [dict] Replaces tags in the schematic. I.e. to insert the git hash or last revision date.
+  # This pre-flight modifies the PCB. Even when a back-up is done use it carefully.
   pcb_replace: 
     date_command: "git log -1 --format='%as' -- $KIBOT_PCB_NAME"
     replace_tags:
@@ -33,6 +34,7 @@ preflight:
   # The report file name is controlled by the global output pattern (%i=erc %x=txt).
   run_erc: true
   # [dict] Replaces tags in the schematic. I.e. to insert the git hash or last revision date.
+  # This pre-flight modifies the schematics. Even when a back-up is done use it carefully.
   sch_replace: 
     date_command: "git log -1 --format='%as' -- $KIBOT_SCH_NAME"
     replace_tags:
diff --git a/kibot/pre_pcb_replace.py b/kibot/pre_pcb_replace.py
index c466e213..9d100a4a 100644
--- a/kibot/pre_pcb_replace.py
+++ b/kibot/pre_pcb_replace.py
@@ -27,7 +27,8 @@ class PCB_ReplaceOptions(Base_ReplaceOptions):
 
 @pre_class
 class PCB_Replace(Base_Replace):  # noqa: F821
-    """ [dict] Replaces tags in the schematic. I.e. to insert the git hash or last revision date """
+    """ [dict] Replaces tags in the schematic. I.e. to insert the git hash or last revision date.
+        This pre-flight modifies the PCB. Even when a back-up is done use it carefully """
     _context = 'PCB'
 
     def __init__(self, name, value):
diff --git a/kibot/pre_sch_replace.py b/kibot/pre_sch_replace.py
index 43454fc9..05571fc0 100644
--- a/kibot/pre_sch_replace.py
+++ b/kibot/pre_sch_replace.py
@@ -31,7 +31,8 @@ class SCH_ReplaceOptions(Base_ReplaceOptions):
 
 @pre_class
 class SCH_Replace(Base_Replace):  # noqa: F821
-    """ [dict] Replaces tags in the schematic. I.e. to insert the git hash or last revision date """
+    """ [dict] Replaces tags in the schematic. I.e. to insert the git hash or last revision date.
+        This pre-flight modifies the schematics. Even when a back-up is done use it carefully """
     _context = 'SCH'
 
     def __init__(self, name, value):