One way to lay curb stones on concrete without using a back support is to use a string line and stakes to create a guide for the placement of the stones. This will help ensure that the stones are laid in a straight line without the need for constant bending over. Additionally, using a rubber mallet to tap the stones into place can help avoid the need for excessive bending and lifting. It's also important to take frequent breaks and use proper lifting techniques to avoid strain on the back. **

To calculate the amount of concrete needed to set 50 meters of curb stones, you will need to consider the depth and width of the trench where the curb stones will be placed. Typically, a trench for curb stones is about 30-40 cm deep and 20-30 cm wide. Once you have these measurements, you can calculate the volume of concrete needed using the formula: volume = length x width x depth. For example, if the trench is 50 meters long, 30 cm wide, and 40 cm deep, you would need approximately 6-8 cubic meters of concrete. It's always best to consult with a professional to ensure accurate calculations for your specific project. **

A professional drill for stone and concrete is a specialized tool designed to effectively and efficiently drill through hard materials such as stone and concrete. These drills typically feature a carbide or diamond-tipped bit that is capable of withstanding the hardness of these materials. They also often have a powerful motor and a sturdy construction to provide the necessary force and stability for drilling into tough surfaces. Additionally, professional drills for stone and concrete may offer variable speed settings and ergonomic features to enhance control and reduce user fatigue during extended use. **

A corner trowel can be purchased at most hardware stores, home improvement stores, or online retailers that specialize in construction tools and supplies. You can also check with local masonry or drywall supply stores, as they are likely to carry corner trowels as well. Additionally, some larger department stores with a home improvement section may also have corner trowels available for purchase. **

The SQL query for the Terra database will depend on the specific task or information you are trying to retrieve. However, a basic SQL query to retrieve all data from a table in the Terra database would look like this: ```sql SELECT * FROM table_name; ``` Replace "table_name" with the actual name of the table you want to retrieve data from. If you want to retrieve specific columns or apply filters, you can modify the query accordingly using the SELECT and WHERE clauses. **

The SQL query for a SQLite database is similar to other SQL databases. Here is an example of a simple SQL query for a SQLite database: ``` SELECT * FROM table_name; ``` This query selects all columns from the specified table in the database. Other common SQL queries for SQLite include INSERT, UPDATE, DELETE, and CREATE TABLE. **

To remove mortar from a trowel, you can use a wire brush to scrub off the dried mortar. You can also use a putty knife or a similar tool to scrape off the hardened mortar. If the mortar is particularly stubborn, you can soak the trowel in a bucket of water to soften the mortar before scrubbing or scraping it off. After removing the mortar, be sure to thoroughly dry the trowel to prevent rusting. **

To apply a trowel finish, start by preparing the surface by cleaning and smoothing it. Then, mix the trowel finish material according to the manufacturer's instructions. Using a trowel, spread the material evenly over the surface in a thin layer, working in small sections at a time. Once the material is spread, use the trowel to create the desired texture or pattern by dragging it across the surface. Allow the finish to dry according to the manufacturer's instructions before applying any additional coats or sealants. **