diff --git a/Exercise-Configuration.md b/Exercise-Configuration.md
index fbe942f..290a7b1 100644
--- a/Exercise-Configuration.md
+++ b/Exercise-Configuration.md
@@ -208,7 +208,14 @@ Pipelines are sent to clients in JSON format and are stored in API in correspond
 Important features:
 
 * Every port either have to have defined reference to variable or it has to be blank. Actual value (for example string) is not allowed in port. If variable name is declared in port it has to exist in variables table.
-* Connection between ports have to always be one end to another end. It is not possible to have one output port which redirects variables to two input ports.
+* Connection between ports have to always be one end to another end. It is not possible to have one output port which redirects variables to two input ports. Of course there has to be exception, it is allowed to have variable which is used only in input port, value of this variable has to be defined in pipeline variables table.
+
+### Boxes
+
+* DataInBox and DataOutBox are special boxes which are treated differently from the others. This means that their deletion or even some breaking changes may have unforseen consequences.
+* Every (except data boxes) box is used only in BoxService for creation purposes and then through abstract Box interface which is of course using inheritance for providing general usage schema. Thanks to this creation of new boxes is quite simple and straightforward.
+
+### Configuration
 
 Mandatory items are bold, optional italic, description of items follows: