This app allows you to insert blocks at the endpoints and midpoints of polylines. You can select as many polylines as you want to insert the blocks. After choosing the polylines, set your preferences in the dialog box.

Choose the block you want to insert from a list that displays all the blocks in the file. Below the list, set the block scale and choose your preferred options: insert at endpoints, insert at midpoints, and align blocks with polylines.

Once you’ve set your preferences in the dialog box, the blocks will be inserted on the polylines (see screenshots for reference).