Fastenings — select the typical overall depth (length) of a standard dog spike used in Indian permanent way practice.

Introduction / Context:
Dog spikes are traditional rail fastenings driven through sleeper holes to clamp the rail foot onto timber sleepers (and historically on some other sleeper types with baseplates). Remembering their common sizes aids quick on-site estimation and exam recall.

Given Data / Assumptions:

• Standard Indian practice with timber sleepers/baseplates.
• “Overall depth” refers to the approximate full length of the spike.
• Nominal sizes are used for ordering and maintenance, with modest tolerance.

Concept / Approach:

Among commonly referenced lengths, a dog spike around 150 mm overall is widely cited for standard duty. While variants exist (e.g., heavier/longer spikes for specific sleepers), 150 mm is the typical benchmark value aligned with exam-oriented standards.

Step-by-Step Solution:

Verification / Alternative check (if short method exists):

Check procurement specs or P.Way handbooks that list standard spike sizes, often 150 mm as a common length.

Why Other Options Are Wrong:

Shorter spikes may not provide adequate holding power; 155.9 mm is not a usual nominal. “None of these” is incorrect since 150 mm is recognized historically.

Common Pitfalls (misconceptions, mistakes):

Confusing dog spikes with screw spikes or elastic fastenings; mixing nominal with exact measured lengths.

Final Answer:

150 mm