chemistry

Guard stone

Guard stone is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Guard stone rather than just read about it. In short: A guard stone, jostle stone or chasse-roue (French, lit. 'wheel chaser'), is a projecting metal, concrete, or stone exterior architectural element located at the corner and/or foot of gates, portes-cochères, garage entries, and walls to prevent damage from vehicle tires and wheels. Description Guard stones were developed as an item of street furniture during the era of horse-drawn vehicles, but some are still in use…

Key takeaways

Guard stone belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Guard stone to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Guard stone from memory before moving on to harder problems.

Reference excerpt

A guard stone, jostle stone or chasse-roue (French, lit. 'wheel chaser'), is a projecting metal, concrete, or stone exterior architectural element located at the corner and/or foot of gates, portes-cochères, garage entries, and walls to prevent damage from vehicle tires and wheels.

Description Guard stones were developed as an item of street furniture during the era of horse-drawn vehicles, but some are still in use today. They are sometimes used as traffic bollards, but are generally positioned to protect a specific object, such as a corner of a building or the side of a gate. In Paris, they are usually metal in the shape of an arc, ball or cone. There are also models in hard stone with a sloping back to guide errant wheels away from impacting a building. Guard stones made of stone were sometimes surrounded by a metal ring to reduce wear. The wheels, including the hub, of horse-drawn vehicles protrude beyond the vehicle's body, and are thus prone to collide with and damage a corner of a building or gate. Today, early guard stones are considered cultural heritage objects and some countries, such as France and Belgium, even protect them under specific heritage regulations. In many cities older guard stones have been replaced by objects designed for automobile traffic, such as curbs and guard rails. In due course guard stones became obsolete and were discarded or reused for other city purposes. When they had been incorporated as part of a building's structure, however, they proved difficult to remove; thus many remain as silent witnesses to early traffic on historic roads. Today such objects are treasured for historical reasons and are often protected as part of a town or city's cultural heritage.

Applications Farmyard entry doors, subject to traffic by heavy horse-drawn carts. Wall corners at the intersection of two city streets (without pavements). In this case, they were often built into the wall. Guard stones made in Haussmann's renovation of Paris. Turns in rural roads or along parapets of bridges. At turns or at intervals on a mountainous ascent. These also helped the coachman to keep the vehicle from rolling backwards, while it paused to let the horses catch their breath.

Gallery

Notes

External links Images of various models of guard stones Archived 2011-07-18 at the Wayback Machine Irish Examiner article related to jostle stone injury, January 2020

Illustrations

Worked examples

Example 1 — a first encounter with Guard stone

Start with the simplest possible case. Write down what Guard stone claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Guard stone before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Guard stone ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Guard stone

In research: Guard stone appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Guard stone in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Guard stone is common in secondary-school and first-year university syllabi. It links to neighbouring topics Architectural elements, Gates, so understanding it makes those chapters shorter.
In everyday life: Look for Guard stone outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Guard stone in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Guard stone means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Guard stone out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Guard stone in simple terms?

Why does Guard stone matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Guard stone?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Guard stone.