The phrase "to take a leap in the dark" refers to taking a risk or making a decision without knowing the outcome, often involving uncertainty or a lack of information. It conveys a sense of courage or recklessness in venturing into the unknown.

The phrase "a snake in the grass" describes someone who is deceitful or treacherous, often hiding their true intentions. It implies that the person may seem innocuous or trustworthy but has a hidden agenda that poses a threat.

The phrase "to blaze a trail" means to be a pioneer or to lead the way in a particular field or area. It often refers to making significant advancements or innovations that others may follow, indicating courage and initiative.

The phrase "by the rule of thumb" refers to making decisions or judgments based on practical experience or general guidelines rather than precise measurements or strict rules. It implies a level of flexibility and reliance on intuition.

"To fool around" generally means to spend time in a lighthearted or playful manner, often without any serious intent.

"Sum and substance" refers to the essential meaning or the most important aspects of a topic or discussion.

"To get into hot water" means to find oneself in a difficult situation or trouble, often due to one's own actions.

"Fight shy" means to be reluctant or hesitant to confront something, often due to fear or apprehension.

"Castle in the air" describes an impractical or fanciful dream that is unlikely to materialize.

"To blow hot and cold" refers to someone who is inconsistent in their attitudes or feelings, often changing from enthusiastic to indifferent.