The sentence "I could not understand what the directions said to do before entering the restricted area" is complex and contains multiple embedded clauses. A complete diagram would be quite large and difficult to represent textually. However, I can provide a description of how to diagram it using traditional sentence diagramming methods. This description will focus on the major components and their relationships.

1. Main Clause: The core sentence is "I could not understand."

• Subject: "I" (placed on the baseline)
• Verb: "could understand" (placed above the baseline, connected to "I")
• Adverb: "not" (placed below "understand")

2. Direct Object Clause: The object of "understand" is the clause "what the directions said to do." This entire clause functions as a noun.

• Pronoun: "what" (placed on the baseline, connected to "understand") This acts as the subject of the embedded clause.
• Verb: "said" (placed above the baseline, connected to "what")
• Direct Object: "to do" (placed above the baseline, connected to "said") This is an infinitive phrase acting as the direct object.
• Subject of "said": "the directions" (placed below "said") This is a noun phrase modifying "said".

3. Prepositional Phrase: "before entering the restricted area" modifies the entire "what the directions said to do" clause.

• Preposition: "before" (placed below the baseline, connected to the entire "what the directions said to do" clause)
• Gerund Phrase: "entering the restricted area" (placed to the right of "before")
  • Gerund: "entering" (placed on the baseline)
  • Object of "entering": "the restricted area" (placed below "entering")

Diagram Representation (Textual Approximation):

Due to the limitations of text, a precise visual diagram is impossible. However, a textual representation attempting to capture the structure would look something like this:

                      I
                 /     |     \
                /      |      \
               /       |       \
              /        |        \
             /         |         \
            /          |          \
           /           |           \
          /            |            \
         /             |             \
        /              |              \
       /               |               \
      /                |                \
     /                 |                 \
    /                  |                  \
   /                   |                   \
  /                    |                    \
 /                     |                     \
Could                  Understand             
       \                |                /
        \               |               /
         \              |              /
          \             |             /
           \            |            /
            \           |           /
             \          |          /
              \         |         /
               \        |        /
                \       |       /
                 \      |      /
                  \     |     /
                   \    |    /
                    \   |   /
                     \  |  /
                      \ | /
                       \|/
                  what the directions said to do
                                      |
                                      |
                                      |
                               before entering the restricted area

This textual representation is a simplified approximation. A true sentence diagram would use lines and branches to show the grammatical relationships more clearly. Software like a Sentence Diagram Generator would be necessary for a proper visual representation.