#include <bits/stdc++.h>
using namespace std;
void solve() {
  string str;
  int arr[1001][1001], first, second, r, c, n, cnt = 0;
  memset(arr, 0, sizeof(arr));
  ;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> first >> second;
    arr[first][second] = 1;
  }
  first = 0, second = 0;
  for (int i = 0; i < 1001; i++) {
    for (int j = 0; j < 1001; j++) {
      if (arr[i][j] == 0) continue;
      if (cnt == n) break;
      cnt++;
      if (i < first || j < second) {
        cout << "NO" << '\n';
        return;
      }
      for (c = first; c < i; c++) {
        str.push_back('R');
      }
      for (r = second; r < j; r++) str.push_back('U');
      first = i;
      second = j;
    }
  }
  cout << "YES" << '\n';
  cout << str << '\n';
  return;
}
signed main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  int t;
  t = 1;
  cin >> t;
  while (t--) {
    solve();
  }
  return 0;
}
